Category: Internet

This Review originally appeared in the July 2026 edition of “StoneSpeak”, the Newsletter of the Southland Geological and Lapidary Club. Below is a slightly expanded version. An Index to this Series of Reviews is here. The Southland Club’s website is here and its Facebook Page is here.  

When I’m searching online for information on a particular stone or mineral, one of the websites that often comes up is Geology.com, a US based site. Its articles tend to be very informative and well-illustrated, always including excellent photos of hand-sized specimens. In fact, a wide range of material can be found there – in its “About” page, it states: “Geology.com is one of the internet’s leading websites for Earth science articles, news about geology, and geographic information. Every day thousands of people visit Geology.com to view our map collection or to read articles about rocks, minerals, gems, and many other Earth science topics.”   

StoneSpeak Newsletter, July 2026.

First page of review article.

The Newsletter contains an ad for this coming week-end’s Club Open Day that I will be attending.

The website is owned by Hobart M. King and run as a family business. According to a Gemological Institute of America article on him, his geological interests began as a six-year-old, hunting for fossils in the limestone driveway at home, and he took up rock tumbling a few years later. He eventually gained a PhD in geology from West Virginia University and a graduate diploma from the Gemological Institute of America. He was employed for many years as a geologist at the West Virginia Geological and Economic Survey and he has also taught geology at university level, mainly at Mansfield University of Pennsylvania (“About the Author” in Geology.com). He is now retired.

Hobart M. King of Geology.com. Source: http://www.gia.edu/gia-news-research/tucson-visit-spurs-geology-professor-publisher-head-back-school.

Geology.com home page.

King became interested in the internet for teaching geology in the mid-1990s. In 2005, he found out that the Geology.com domain, originally owned by a petroleum consulting company, was up for auction. “I went home and told my wife I wanted to buy the website,” he recalls, “so we scraped together as much money as we could and actually won it in the auction” (Google Adsense article). Geology.com has become a family business, with King’s wife, sister, daughter and nephew each working in various roles. He also owns and operates RockTumbler.com (the subject of a later review).

Geology.com has an online store for a wide range of geology and stone-related goods. For example, there is an extensive offering of books on a range of topics such as  geology, rocks, minerals, gemstones and fossils. Also for sale are rock and mineral kits and tumbled stones. From the beginning, King decided to accept commercial ad traffic on his websites because of the revenue it generated. He uses Google AdSense. He notes that “AdSense is about 50% of our profit and still the most profitable part of our business today” (Google Adsense article). I find that when I use the website, the ads are noticeable but not too intrusive – they tend to be down the lefthand page margin or at the bottom of the screen. Even now and then a page is interrupted by an ad that can easily be dismissed with one click. The quality of the information and illustrations of stones and minerals easily outweighs any annoyance, in my experience.

“Rocks” page, Geology.com.

“Minerals” page, Geology.com.

“Gemstones” page, Geology.com.

Part of “Rocks” page, Geology.com.

Part of Gemstones” page, Geology.com.

Article on flint, chert and jasper, Geology.com.

The “Rocks” section of Geology.com begins with links to pages of photos for igneous, metamorphic and sedimentary rocks. Then there are pages on 45 different rocks, from andesite and basalt through to shale and siltstone. This coverage is limited and maybe will be expanded in the future. Argillite, for example, is not currently included, with siltstone being the closest category. Chert is included but not jasper – through the chert page has a link to an article entitled “Flint, Chert, and Jasper: Names for Microcrystalline Quartz”.    

The “Minerals” section is a lot larger, with a list of 90, from andalusite, anhydrite and apatite all the way to vesuvianite, zircon and zoisite (which includes thulite). The “Minerals” main page also contains links to articles on such topics as fluorescent minerals, using acid for testing, mineral hardness, and streak testing. If you can’t find something in the “Rocks” or “Minerals” section, check out “Gemstones” which includes over 120 entries including amethyst, nephrite and even dinosaur bone.

The home page lists a number of categories of “Geology and Earth Science News and Information”. Here, articles can be found on such topics as plate tectonics (15 articles), fossils (17 articles) and meteorites (19 articles). The coverage is global, not focused just on material from the United States.

In conclusion, Geology.com content is written by a specialist in geology and gemology but with non-specialists firmly in mind. It covers some technical detail relating to a rock or mineral but I find that it is always explained clearly and technical jargon is avoided. Usually I wish a bit more information had been included but what is there is very useful.

The next Review in this Series is not yet available. 

This Review originally appeared in the June 2026 edition of “StoneSpeak”, the Newsletter of the Southland Geological and Lapidary Club. Below is a slightly expanded version. An Index to this Series of Reviews is here. The Southland Club’s website is here and its Facebook Page is here.

When I was looking for good introductory material about trace fossils three years ago, I came across an excellent article “Someone passed this way: Tracks, trails, impressions, and footprints” on the “Geological Digressions” website. I liked the turn of phrase used there: “Trace fossils are what is left of the activity of some ancient critter”. It turned out that the site is produced by a retired New Zealand geologist, Brian Ricketts.  

Home Page of “Geological Digressions” http://www.geological-digressions.com.

Trace Fossils article on “Geological Digressions” http://www.geological-digressions.com/someone-passed-this-way-tracks-trails-impressions-and-footprints

From Trace Fossils article on “Geological Digressions” http://www.geological-digressions.com/someone-passed-this-way-tracks-trails-impressions-and-footprints

Ricketts first studied geology at the University of Auckland in the early 1970s and did his doctoral degree in the Canadian Arctic. He then worked for the Geological Survey of Canada (GSC) for a few years. “I quit the GSC in 1997 and moved with my Canadian family back to Aotearoa–New Zealand to work a 4-year teaching stint at the University of Waikato.” But “with an evolving disenchantment of academia, I decided to form my own consulting company in 2005 – a company of one – and never looked back!” (quotes taken from “A Geological Life” on the website). During his time as a geologist, he also worked in Hungary, Chile, Australia, USA, the United Kingdom and the Netherlands. Retired now, Ricketts spends time on his Waikato organic kiwifruit orchard but also continues the development of “Geological Digressions”. More details on his background can be found in “A Geological Life”.

Ricketts started his website in December 2015. He states there that “I do this for the love of it. I do not receive any remuneration for the site (and I don’t advertise). The website is not attached or beholden to any organization.” The main part of the site is a “Virtual Classroom” containing material on sedimentology, stratigraphy, volcanology, geological structure, sedimentary basins, petrography and petrology – this is aimed primarily at university undergraduate students. There is a lot of material here – 23 Main Sections, each with numerous articles – and often useful links are made to other sources as well as related pages in “Geological Digressions”.  

“Virtual Classroom” Page http://www.geological-digressions.com/how-to-do-field-tasks.

“Bivalve morphology for sedimentologists” http://www.geological-digressions.com/bivalve-morphology-for-sedimentologists

“Ripple Lithofacies – Ubiquitous Bedforms” http://www.geological-digressions.com/ripple-lithofacies-ubiquitous-bedforms.

For example, in the Virtual Classroom Main Section “Minerology of Sandstones”, there are 20 articles, one of which is on “Bivalve morphology for sedimentologists”. It looks at bivalve fossils in detail, including their external and internal morphology, and shell orientation, with well-labelled illustrations. One of the other Main Sections is “Lithofacies”. Lithofacies refers to the physical and compositional characteristics of a sedimentary rock unit or sediment layer. There are 41 articles in the Section, one of them being “Ripple Lithofacies – Ubiquitous Bedforms”. It describes how ripples are formed on sedimentary surfaces and their different characteristics.   

This “Virtual Classroom” is an excellent resource for people who have not formally studied geology – here you can get access to some of the material that is presented to university students. Yes, it can be technical, but it is well presented and a treasure for the keen learner.    

Other articles in “Geological Digressions” are written with non-specialist or non-technical people in mind. Across the top of the site’s pages are links to four groups of articles: Glossary, Atlas of Sediments, Ancient Earth, and More. There are 11 glossaries (alphabetical lists of technical terms with their meanings), on topics including Stratigraphy, Sedimentary Structures, Volcanics, and Palaeontology. Alongside the explanations of key terms are links to any website articles relevant to them. “Atlas of Sediments” is a collection of photos that Ricketts has accumulated. There are 24 groupings here. One of them, for example, is “Atlas of Trace Fossils” which has 33 photos of different trace fossils, some from New Zealand.

One of the Glossaries http://www.geological-digressions.com/glossary-paleontology.

“Ancient earth. 2 How old is it?” http://www.geological-digressions.com/ancient-earth-how-old-is-it.

Sandstone formation http://www.geological-digressions.com/from-sand-to-stone-sandstone-a-remarkable-transformation.

The “Ancient Earth” heading takes you to 13 articles. The second one asks how old the Earth is. Here, Ricketts looks at a number of people in history who have attempted answers. He then refers to the search for the oldest rocks on Earth and what they imply. Another “Ancient Earth” article is on stromatolites, the earliest physical life form on Earth. Under the “More” heading are 14 other topics, some of which contain a lot of different articles. For example, “Interpreting Earth” has 28 articles, ranging from how sand gets turned into stone to understanding how a fossil forest in the Arctic has survived.

As you can see, “Geological Digressions” is large, detailed, diverse and wide-ranging, containing both technical and non-technical geology-related information broadly defined. The Home Page refers to “436 articles” being there. In general, these are well-written and have lots of interesting detail and illustrations. You can use the “Search” function to look for something specific. Or you can take a stroll along its many corridors, exploring whatever takes your fancy.

The next Review in this Series is of Three Kiwi “YouTube” Rockhounds. The Series Index is here. 

This Review originally appeared in the April-May 2026 edition of “StoneSpeak”, the Newsletter of the Southland Geological and Lapidary Club. Below is a slightly expanded version. An Index to this Series of Reviews is here. The Southland Club’s website is here and its Facebook Page is here.

Anyone can used their phone camera to take photos and make video clips of their activities and post them on social media. Facebook, Instagram and YouTube are popular outlets and some rockhounds have not been reluctant to use them. They provide a great way to store images of a find or a fossick that you can go back to anytime to enjoy. And other people can enjoy and learn from them too. Here is a review of how three New Zealanders have used YouTube to store and share their videos of stones and fossils.

Nicola Gray, who lives in Hastings, Hawkes Bay, has a Facebook Page and YouTube channel, and she is active on a number of Facebook Rockhound Groups. Her YouTube channel “New Zealand Rockhound” documents many of the details of her fossicking and tumble-polishing, as well as stone cutting and craftwork. Introducing herself on YouTube, Nicola states: “I love rock hunting, and especially love sharing my finds with others. I really enjoy sharing my rock tumbler barrel washouts. I make beautiful pendants from my stones too.” For Nicola, making and editing and posting videos are a regular and natural part of being a rockhound.

Nicola Gray’s YouTube Channel http://www.youtube.com/channel/UCSQMZ5-H0nsBL_bM2BjNEHw/videos.

Nicola Gray’s videos.

More of Nicola Gray’s videos.

I first met Nicola when she travelled south with Angie Nicholas to visit Gemstone Beach in April 2023. At the time I was nearing the end of my “Southern Sojourn” on the south coast. Our first joint fossick there is described by me in this Post and this Post, with two further fossicks described here and here. Nicola’s own video of visiting Gemstone Beach can be found here – it is just over eight minutes long and has been viewed over 3,100 times.

At the time I wrote this Review, in early April 2026, Nicola’s channel contained 479 videos and had 1,130 subscribers. I went through her latest 50 videos to identify their content. I found that in 12 of them, Nicola was showing different types of stones, sometimes recently arrived in the mail from other people, sometimes recently tumbled/cut or about to be tumbled/cut. Another 12 of her latest 50 videos showed Nicola washing out a tumble barrel or vibratory tumbler. Nine showed her cutting stones, and eight recorded her looking for stones on a beach somewhere in New Zealand (such as in Hawkes Bay, on the south coast including Gemstone Beach, and the West Coast). The other nine videos were on topics such as loading a tumbler barrel, tumbling advice, and a microscopic view of a stone.

At the top of the list of videos on a YouTube channel, you can click on “Latest”, “Popular” and “Oldest” to help you move among them in different ways. Nicola’s most popular video, viewed 30,878 times, is a short 33 second clip posted in October 2020 recording her discovery of a storm jasper in the Tukituki River. Most of Nicola’s videos are between about three minutes and 12 minutes in length with only the odd one lasting more than 20 minutes. So, in many ways, they are snapshots into the daily life of a rockhound who cuts and polishes her finds.

Gordon Sherwood and his wife Beth have a crystal and wellness shop in Edgecumbe, Bay of Plenty, called Heaven’s Ascent. Gordon has a Facebook Page under the title of “New Zealand Rocks Downunder” which is also the name for his series of YouTube videos. He introduces himself as follows: “I live in the Eastern Bay of Plenty, and have to travel to other areas for older rocks that contain interesting specimens.  You can expect to accompany me as I find interesting rocks, fossils, and uncover some of the interesting insect life here in New Zealand. Look out for my attempts at cutting and carving the rocks that I have found as I get the gear together to do it… Our retail shop has a great selection of crystals and gemstones that fuels this passion to fossick, which is squeezed in whenever I can, going AWOL without getting in too much trouble with the Mrs.” In July 2025, Gordon and Beth featured in an Eastern Bay article celebrating National Tartan Day.

Gordon Sherwoods YouTube Channel http://www.youtube.com/@NewZealandRocksDownunder/videos.

Gordon Sherwood’s videos.

Source: https://easternbayapp.co.nz/news/articles/6865b5eb80a872f72cee39b5

Gordon has had some health issues which sometimes delays new postings. However, at the time I wrote this Review, his YouTube channel contained 138 videos and had 2,030 subscribers. His most popular video, “Uncovering the Secrets of Gemstone Beach” (33 minutes long), was posted in August 2023 and has been viewed 48,315 times. Gordon’s videos tend to be longer than Nicola’s, usually between 15 and 30 minutes. There is more of a narrative to each piece and they are often quite informative about a stone type or fossicking place. Some topics are: excavating microfossils at Matata Beach (a favourite destination), visiting the Tauranga Gem and Mineral Club 2024 Show, searching for pounamu greenstone at Jackson Bay, looking for pakohe (a traditional stone used for tool making and carving), fossicking at Birdlings Flat, and fossil hunting at Motunau Beach.

The third YouTube user is Morne of “Mamlambo Fossils” whose first video was posted in May 2019. He has become very well-known: Newsweek had an article on “Morne Mamlambo” in June 2021; TV1’s Seven Sharp had a five-minute feature on him, shot on Motunau Beach, in November 2024 , reporting that he had rented a hall at the old Waikuku School in Canterbury as a workshop, fossil museum and educational centre; and on 30 March this year RadioNZ interviewed him in their Monday Afternoon Expert segment.

Morne, who declines to give his surname, is a software engineer and grew up in South Africa, He introduces himself as follows: “I’m an amateur fossil hunter living on the South Island of New Zealand. I enjoy hunting the coastal cliffs for Miocene and Cretaceous era fossils and venturing further afield for the petrified wood and fossils that can be found there. I’m constantly learning about the fossils that can be found here in New Zealand. I also use a variety of tools and techniques to prepare the fossils I find which I then donate to New Zealand museums.” He has taken the name “Mamlambo” from a mythical South African creature which has the head of a horse, the lower body of a fish, short legs, and the neck of a snake. He started off by taking videos of his finds to show his family back in South Africa and attracted quite a bit of attention when he posted them on YouTube.

Morne Mamlambo’s Fossils Channel http://www.youtube.com/@MamlamboFossils/videos.

Morne Mamlambo’s Rocks Channel http://www.youtube.com/@mamlamborocks/videos.

Guided fossil walks offered https://mamlambofossils.com/fossiltours.

Morne has a number of online and social media outlets, including a website, and he posts videos on all of these. One of the things on his website is his offer of paid guided fossil walks. At the time I wrote this Review, his “Mamlambo Fossils” YouTube channel contained 370 videos and had 611,000 subscribers. His videos record his hunts for fossils, the many hours he spends preparing them (using a variety of tools to wear away the surrounding rock), and issues around their identification. One of his most popular videos from 2021 “MONSTER fossil crab prep – the 50lbs crab finally gets prepped… and it’s a beast!” is 13 minutes long, has been viewed 2,443,525 times, and uses speeded-up photography to show the 208 hours of work he spent revealing the fossil. He has made lots of fossil finds, many of them very significant, such as a new species of billfish, now officially named Zealandorhynchus fordycei, honouring the late Ewan Fordyce, an influential University of Otago vertebrate palaeontologist.

Morne also has a second but smaller YouTube channel called “Mamlambo Rocks”. It contains 50 videos and has just over 10,000 subscribers. The most popular of these videos are on agate hunting in Canterbury. There is also a 48 minute video of most of an August 2025 talk on agates by the late Malcolm Luxton. Other videos feature petrified wood and fossicking in such places as Birdlings Flat and the Conway River.

It takes time to view a video online – you can’t just glance at it like you can a still photograph. And you don’t know how interesting or useful it will be until you’ve seen it through. But a good video can take you right into a promising rockhunting area, and show you what to look for, much more effectively than just written text. Watching a couple of their homemade videos allows you to assess if the approach of a rockhound works well for you, providing enjoyment and learning and inspiration.

“Thank you!” to these three rockhounds for sharing their passion and knowledge with us.

The next Review in this Series is of the New Zealand-based “Geological Digressions” website. The Series Index is here. 

This Review originally appeared in the March 2026 edition of “StoneSpeak”, the Newsletter of the Southland Geological and Lapidary Club. Below is a slightly expanded version. An Index to this Series of Reviews is here. The Southland Club’s website is here and its Facebook Page is here.

When I’m doing some research on a rock or a mineral, I usually look at the relevant entry in the “AlexStrekeisen” website. Some of the information there is quite detailed and often accompanied by good photos of rocks.

Cover of “StoneSpeak” March 2026.

Page 7 of “StoneSpeak” March 2026.

Home page of http://www.alexstrekeisen.it/english/index.php

Alessandro Da Mommio. Source: http://www.alexstrekeisen.it/english/index.php

There are also microphotos of thin rock sections at the end of each entry – photos of what you’d see looking through a microscope. These are intriguing and can be quite spectacular:

Calcite and zeolite (grey) filling an amygdale. Field of view = 7mm. http://www.alexstrekeisen.it/english/vulc/amygdales.php

Fragments of various nature in a breccia, field of view = 7mm. http://www.alexstrekeisen.it/english/sedi/breccia.php

Olivine crystals in a dunite, field of view = 7mm. http://www.alexstrekeisen.it/english/pluto/dunite.php

Allanite crystals, biotite and microcline feldspar in a granite, field of view = 7mm. http://www.alexstrekeisen.it/english/pluto/allanite.php

Globigerinids Foraminifera in a Mudstone, field of view = 2mm. http://www.alexstrekeisen.it/english/sedi/mudstone.php

Hornblende, plagioclase and quartz in a type of gabbro, field of view = 7mm. http://www.alexstrekeisen.it/english/pluto/quartzgabbro.php

Alessandro Da Mommio is the Italian geologist behind this website (photo at top of Post, far right). He notes on the home page that his passion for optical petrography inspired him to create an online vehicle for “the recognition and identification of mineral phases in thin section”. The website is available in both Italian and English. If you find yourself on the Italian-language version of the site, click on the Union Jack flag just under the header to be taken to the English-language version.

The website is named after Albert Strekeisen (1901-1998), a pioneering Swiss petrologist who has been very influential in rock classification systems. The QAPF (Quartz – Alkali feldspar – Plagioclase – Feldspathoids) diagram for the classification of igneous rocks is known as the “Streckeisen diagram” in his honour (see image of diagram below, far left). Da Mommio is a geology lecturer at the University of Milan and a specialist in microphotography. Last year, with Victoria Pease he published the book “Atlas of Minerals and Igneous and Metamorphic Rocks in Thin-Section”.

“Streckeisen diagram”, the QAPF diagram for classification of igneous rocks. https://commons.wikimedia.org/wiki/File:Streckeisen_Plutonic_Rocks.svg

Rhodonite page. http://www.alexstrekeisen.it/english/meta/rhodonite.php

Rhodonite, Franklin Mine, New Jersey. http://www.alexstrekeisen.it/english/meta/rhodonite.php

Granular rhodonite crystals, field of view = 7mm. http://www.alexstrekeisen.it/english/meta/rhodonite.php

Da Mommio describes his website as follows: It is “designed for students of geology and petrography and geology enthusiasts… Each page consists of two parts, descriptive (an exhaustive explanation of the mineral phase) and visual (high-resolution photographs).” New pages on rocks and minerals are being added regularly – one of the most recent is Rhodonite which has especially colourful thin-section microphotos (see image above, far right).

The website has five main sections – on the four main types of rocks (plutonic, volcanic, metamorphic and sedimentary) and on the Italian magmatic provinces (areas of volcanic rocks). The rock sections have long lists of contents running down the left margins, arranged under a small number of headings. For example, for Metamorphic Rocks, the main headings are Metamorphic minerals, Texture and microstructure, and Metamorphic rocks. For Sedimentary Rocks, the main headings are Sedimentary rocks [main types], Turbidites, Fossils, Sedimentary minerals, Texture, and Rocks. For each entry under those headings, there is usually a description of the mineral, rock or item, often with technical detail.

Page on Metamorphic Rocks. http://www.alexstrekeisen.it/english/meta/index.php

Page on Sedimentary Rocks. http://www.alexstrekeisen.it/english/sedi/index.php

Page on Plutonic Rocks. http://www.alexstrekeisen.it/english/pluto/index.php

However, the entries vary in length and usefulness, some being quite detailed but others being quite short. A few of the entries rely heavily on Mindat.org, but most go beyond that. Unfortunately, the list of references for minerals and rocks seem to be mainly textbooks, not online sources that you can follow up. For that, you then need to go to such websites as Geology.com and Wikipedia.

The next Review in this Series is of three New Zealand YouTube rockhounds. The Series Index is here. 

I wrote this Review for the December 2025 edition of “StoneSpeak”, the Newsletter of the Southland Geological and Lapidary Club. The following is a slightly fuller version. The Southland Club’s website is here and its Facebook Page is here.

I was recently doing some research about breccia for a couple of blog posts I was writing (“TumbleStone Calendar 2026: November – Breccia” and “T is for a Type of Tiny Tectonic Breccia?”). By far the best piece I found on breccia was on a website called Sandatlas. The piece is well-written, comprehensive, nicely illustrated, is not shy about being a bit technical but is generally quite readable, and it covers a wide range of relevant issues. It is not a brief piece and it doesn’t oversimplify, but it was invaluable in helping me gain a detailed overview of breccia and its formation. The accompanying photographs and diagrams are outstanding. The rest of Sandatlas is similar.

Siim Sepp. https://sandatlas.org/about

Sandatlas Home Page. https://sandatlas.org

Sandatlas page on Breccia. https://sandatlas.org/breccia

Sandatlas is the project of Siim Sepp (above, left), an Estonian who describes himself as a software developer, author, geologist, and photographer. He started Sandatlas in 2012 as a website about sand. But what started with photographing sand samples from around the world grew into a broader guide to geology. The website’s home page now states: “Sandatlas is an educational website that aims to explain geological concepts in a clear and accessible way. The content is designed for students, educators, amateur geology enthusiasts, and anyone curious about the Earth’s materials and processes. The site features illustrated articles about rocks, minerals, sand types, and key geological terms – supported by original photographs to help readers better understand the subject matter.”

One of the great things about Sandatlas is Sepp’s high-resolution photos of rocks – he often provides a good range of examples of a rock type, and they tend to be handful size or just a bit bigger, the size you find on a beach or in a river. The majority of the photos featured on Sandatlas are from Sepp’s own rock and mineral collection, assembled from numerous geological expeditions to places including Estonia, the Nordic countries, the United States, Cyprus, Morocco, France, and Ireland.

Gabbro specimen. https://sandatlas.org/gabbro/

Another gabbro specimen. https://sandatlas.org/gabbro/

A further gabbro specimen. https://sandatlas.org/gabbro/

One of the main pages on Sandatlas is “Complete Guide to Rock Types: Igneous, Sedimentary, Metamorphic”. Forty-six igneous rocks are listed, with brief descriptions, and 30 of them have links to their own page with a more detailed description and lots of interesting photos. Thirty sedimentary rocks are listed (19 having their own page), and 27 metamorphic rocks (16 with their own page). I assume Sepp intends eventually to provide pages for all the listed rock types. In general, the coverage is selective but is nevertheless impressive.

Igneous rocks. https://sandatlas.org/types-of-rocks/

Sedimentary rocks. https://sandatlas.org/types-of-rocks/

Metamorphic progression. https://sandatlas.org/metamorphic-rocks/

Another main page is “Rock Forming Minerals”. This is a very long page and is much more technical than the rock types section. It’s more like what you would find in a geology textbook, but in my view it is well organised, well explained and well illustrated. If you want to gain an understanding of the chemistry and character of something like framework silicates, or the garnet group, or corundum, this is a great place to go to. How and where minerals form is covered along with the general traits of hand specimens. Field tips, weathering and environmental notes are usually provided. These help to make the technical information more useful to the likes of you and me.

There’s a lot 0r interesting stuff on Sandatlas, although it’s not always easy to find. At the end of the home page is a list of articles that explain key geological concepts and natural processes. This includes such intriguing topics as “How Geologists Identify Rocks”, “What is Opaque Color”, and “Do Rocks Really Fit Into Three Categories?”. At the end of each article is a folder icon with one or two names of Sections in the website – if you click on these Section names, you will be taken to lists of other articles that are otherwise hard to identify.

Sandatlas article. https://sandatlas.org/how-geologists-identify-rocks/

Sandatlas on the 3 categories of rocks. https://sandatlas.org/rock-classification-problems/

Two Category Names for lists of articles at end of Sandatlas on the 3 categories of rocks. https://sandatlas.org/rock-classification-problems/

“Rocks are not silent,” writes Sepp in the “About” page of Sandatlas. “They carry the memory of oceans long vanished, volcanoes that once shook the sky, continents that drifted across the planet. Learning to read them is a way of regaining closeness to the Earth. When we look at nature with understanding rather than indifference, we begin to value it – and we protect what we value.” He continues: “Sandatlas is a bridge between curiosity and knowledge, between observation and insight. It… exists for the broad community of curious minds – hikers who pause at a cliff face, photographers drawn to patterns in stone, collectors who turn over pebbles just to know what they are. It is here for anyone who suspects that the landscapes they walk through are more than just scenery.”

The next in this Series is “A Review of ‘New Zealand Geographic’ Magazine Online“. An Index to this Series is here.

I wrote this Review for the October 2025 edition of “StoneSpeak”, the Newsletter of the Southland Geological and Lapidary Club. The following is a slightly fuller version. My first Review of an online resource for “StoneSpeak” was of Peter Ballance’s e-book (2017) “New Zealand Geology: An Illustrated Guide”. The Southland Club’s website is here and its Facebook Page is here.

Page 1 of “StoneSpeak” Newsletter, October 2025.

Page 5 of “StoneSpeak” Newsletter, October 2025.

Page 6 of “StoneSpeak” Newsletter, October 2025.

This website (https://rocksminerals.flexiblelearning.auckland.ac.nz) was produced by the University of Auckland’s Department of Geology in 2005. It provides very good introductory information about minerals and rocks in a New Zealand context. The language used manages to avoid over-simplification and usefully explains many key technical terms about geology and rocks. For example, on Clastic Sedimentary Rocks: “The fragments of pre-existing rocks or minerals that make up a sedimentary rock are called clasts. Sedimentary rocks made up of clasts are called clastic (clastic indicates that particles have been broken and transported). Clastic sedimentary rocks are primarily classified on the size of their clasts” (see first photo below). The website is illustrated with a number of photos of mineral and rock specimens from the University’s Geology Department collection.

When I find a stone on a beach, I often go to Jocelyn Thornton’s book “Gemstones” for help to identify it. Or I post a photo on a New Zealand rockhound Facebook Group, asking for an identification. Often I get a name for the stone, such as argillite or gabbro. I can then go to this University of Auckland website, a more geology-oriented source, to get some information on argillite or gabbro.

On clastic sedimentary rocks. https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/sedimentary.html

Argillite. https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/argillite.html

Gabbro. https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/gabbro.html

There are five sections in this website: Home, The Geology of Auckland, Minerals, Rocks, and Glossary. I have most often consulted the Minerals and Rocks sections to gain an understanding of the types of stones I find on the beach. The most useful parts of the Minerals section are Properties (eight are outlined) and Common Rock-Forming Minerals (21 are described). One of the limitations of the website can be seen here – it doesn’t always do a good job of dealing with the range of types of a mineral or rock (always a difficult task). So its photos of Garnet, for example, are all of one type and don’t include the likes of grossular and hydrogrossular.

https://rocksminerals.flexiblelearning.auckland.ac.nz/minerals/physical.html

https://rocksminerals.flexiblelearning.auckland.ac.nz/minerals/common.html

https://rocksminerals.flexiblelearning.auckland.ac.nz/minerals/index.html

The Rocks section includes important Features to look for when writing descriptions and identifying rocks. To take Texture as an example: “Texture refers to the shape, arrangement and distribution of minerals or grains / clasts within the rock – the texture in a geological sense does NOT refer to the roughness of the surface of the rock”. Then 12 igneous, eight sedimentary and seven metamorphic rocks are described. These entries include a basic description, photos of usually one to four specimens (up to seven in a couple of cases), and a list of basic properties. I especially like the chart that is a guide to the identification of igneous rocks based on their mineral composition.

https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/index.html

https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/igneous.html

https://rocksminerals.flexiblelearning.auckland.ac.nz/rocks/metamorphic.html

I use this website whenever I want to check out a particular mineral or rock. Its New Zealand focus is its strength, along with its careful balance of technical detail and understandable explanation. I always want it to provide more information, and I wish it had more photos of specimens, but this doesn’t detract from its value.

The next Review in this Series is of Jocelyn Thornton’s (1985) “Gemstones”. An Index to this Series is here.

I wrote this Review for the August 2025 edition of “StoneSpeak”, the Newsletter of the Southland Geological and Lapidary Club. The following is a slightly fuller version. My first Review of an online resource for “StoneSpeak” was of Peter Ballance’s e-book (2017) “New Zealand Geology: An Illustrated Guide”. The Southland Club’s website is here and its Facebook Page is here.

Mindat Home Page http://www.mindat.org

Jolyon Ralph, 2024. http://www.mindat.org/user-1.html

Mindat chalcedony page http://www.mindat.org/min-960.html

The website www.mindat.org describes itself as “the world’s leading authority on minerals and their localities, deposits, and mines worldwide”. Wikipedia describes it as “the largest mineral database and mineralogical reference website on the Internet”. I assume its name is a shortening of the phrase “mineralogical data”. The mineral entries, localities, and photographs in Mindat are really useful material even if you aren’t interested in a lot of the technical detail and resources in it. Mindat is not a website that will help you identify a stone you have found while fossicking. But once you have an idea of what mineral is in the stone, Mindat will tell you all about that.

Mindat is the brainchild of Jolyon Ralph, an Englishman. His story of its origin starts: “On Christmas Day 1993, there was nothing good on television. So I went upstairs to my room and started writing mindat”. He was 23 years old, and trying to produce mineralogical information in an accessible form. It was initially a personal computer database. He then uploaded it onto the internet as a website in October 2000. At the same time, it became a community-editable venture – other people could contribute material. Contributors to the database are vetted to ensure the accuracy of their material and expert knowledge. The history of Mindat as a website can be found here. Ralph was awarded the Mineralogical Society of America’s Distinguished Public Service Medal in 2011 for his work on Mindat (see here for a shaky and sometimes blurry YouTube video of the award presention). In 2014, Mindat was transferred to the Hudson Institute of Mineralogy who have operated it since.

Part of chalcedony page on Mindat http://www.mindat.org/min-960.html – more chalcedony photos at http://www.mindat.org/gm/960

Part of chalcedony page on Mindat http://www.mindat.org/min-960.html

Part of chalcedony page on Mindat http://www.mindat.org/min-960.html

The main strength of Mindat is the information it provides on different minerals. It includes useful descriptions as well as a lot of technical detail. However, the amount of information varies depending on how much work has been done on the entry. For example, “Chalcedony” is well-developed but “Hydrogrossular” is quite thin. Standard entries have a selection of photos at the top with links to more images, something I have used quite a bit. Entries have sections on such topics as physical properties, optical data and fluorescence, crystallography and crystal structure, chemistry, varieties, localities, and references.

Mindat page on hydrogrossular http://www.mindat.org/min-1974.html

Mindat page on hydrogrossular http://www.mindat.org/min-1974.html

Top half of review in “StoneSpeak”

The references provided by Mindat include key documents on a mineral and usually have URL links to download them – that is how I got access to Colin Hutton’s 1943 article on hydrogrossular where he first described it from samples in Nelson. The localities for a mineral don’t cover all places it can be found but usually just the most significant. For hydrogrossular, four New Zealand localities are recorded (despite the map initially showing only three): two in Northland, one in Marlborough and one on the West Coast. Te Waewae Bay (Gemstone Beach), where I find my hydrogrossulars, is not mentioned. As stated in a review of Mindat for educators and students, “Although this database is maintained and enriched by an army of volunteers who strive to ensure the accuracy of the data, you may still want to consult one or two other sources to cross check the information.”

The next Review is of the University of Auckland’s “Geology: Rocks and Minerals” Website. An Index to this Series is here.