Category: Jasper

This is a slight expansion of my letter “O” contribution to the current Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. In the 2021 version of this Series I posted “O is for Opaque Orepuki Orbicular Jasper” which featured a different type of orbicular jasper, a hematite poppy jasper.

O is for Outstanding Orepuki White Orbicular Jasper

White orbed jasper, Gemstone Beach.

Other side of white orbed jasper.

I found this small stone on Gemstone Beach, Orepuki, in March this year. This Post describes the fossick during which it was found, and it includes some information on orbicular jaspers. This Post shows the stone after tumble polishing. It is the only white orbicular jasper I have found on the Te Waewae Bay coast so far, with the red orbed poppy jasper more common. GeologyScience states: “Orbicular patterns form due to the presence of various mineral impurities or inclusions within the silica solution. These impurities can include minerals such as hematite, goethite, chlorite, or other oxides and hydroxides, which crystallize in concentric layers around a nucleus or central point, giving rise to the orb-like structures.” The orbs in orbicular jasper can consist of concentric circles, spherical shapes, or irregular spots, and can vary widely in size, colour, and arrangement. “A Selective Annotated Index to Poppy Jaspers in TumbleStone Blog” lists Posts that contain stones displaying this diversity.

The next Post in this Series is “P is for Pink”. An Index for this Alphabetical Series is here.

This is my tenth contribution to the current Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. In the 2021 version of this Series I posted “J is for (Picture) Jasper”.

J is for Jasper

I found this little two-centimetre-long stone on Gemstone Beach, Southland, in February 2023. It’s a red and white jasper with what I guess is white and translucent chalcedony veins. When I picked it up, I could see it was interesting but couldn’t make out the details. The close-up photos, produced through cropping, have clarified the stone’s composition. As you most likely know, jasper is usually the term for a type of chalcedony (microcrystalline quartz) – it is opaque due to the presence of minerals which give it colour, with the red of iron oxide being most common. As Stonemania puts it: “The presence of iron oxides, often from hematite, turns jasper red. Clay minerals can cause a yellowish, white or grey colour, while goethite introduces yellows and browns. Chlorite usually turns jasper green”. Other minerals may also provide jasper’s colour. Jasper is usually classified as sedimentary, precipitating from solutions moving through the ground. Note that “jasper” is sometimes used for non-chalcedony stones, such as bumblebee jasper which Mindat calls a fibrous calcite.

The next Post in this Series is “K is for Kai Iwi Beach Stone”. An Index for this Alphabetical Series is here.

This is a slightly expanded version of my nineth contribution to the current Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. In the 2021 version of this Series I posted “I is for Ichnogenus Protovirgularia”, a trace fossil stone.

I is for Intrusive Igneous stone.

I quite like the black-and-white spotted stones I find on Gemstone Beach and elsewhere along the Te Waewae Bay coast. They are not breccia (made up of fragments or clasts) and are not amygdaloidal (infilled gas bubble holes), but have tiny white crystals. The size, shape and distribution of the white crystals can vary considerably, as illustrated with Stones W43 to W61 in this Post. And they can, of course, be found in other parts of New Zealand. I found this one on 3 August this year on Gemstone Beach. Stones like this are likely to come from igneous rock that has cooled while being below the surface of the Earth – this is also known as plutonic, after Pluto, the Roman god of the underworld. Its solidification takes a long time so crystals have time to grow bigger, large enough to be seen with the naked eye. By contrast, in extrusive volcanic rock which cools a lot more quickly, crystals have little time to grow and are often visible only under a microscope. See Geology.com for a good introduction to igneous rocks. The commonest intrusive igneous rock is granite. Others include gabbro and diorite (see the diagram at the end of University of Auckland Geology) which are said to occur on the Te Waewae Bay coast but I have not yet worked out how to identify them.

The next entry is “J is for Jasper”. An Index for this Alphabetical Series is here.

This is a slightly expanded version of my eighth contribution to the current Alphabetical Series in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”. In the 2021 version of this Series I posted “H is for Hematite Jasper”, a brecciated stone.

H is for Hematite Poppy Jasper

Very small hematite poppy jasper.

Other side of stone.

I found this very small stone on Gemstone Beach on 19 March this year. It’s the size of my small fingernail. I often collect small stones because they play a role in the mix of stones in a tumble-polish barrel. When I picked this one up on the beach, I thought there was something going on inside it but couldn’t really tell with the naked eye. The photos reveal a special composition, an unusual kind of poppy jasper. Such small bright red jaspers can be found on Gemstone Beach and nearby. Not all of them are poppy jaspers. They stand out when wet, and practically glow in the sun. They have a more intense brightness than other red jaspers because, I suspect, of the hematite in them. Hematite (haematite) is a kind of iron oxide known for its distinctive reddish-brown to silvery or black metallic colour. The origin of the term lies in the Greek word for blood. Geology.com has a very good section on hematite, noting that it is one of the most abundant minerals on the Earth’s surface and is a very common constituent of rocks.

The next entry is “I is for Intrusive Igneous Stone”. An Index for this Alphabetical Series is here.

I once mentioned in a Post on “small stones” that they are invaluable to the tumble polisher. In a rotating barrel, small stones “carry” the grit or polish to the larger stones, fill up the spaces between them, and balance the load. Some small stones are striking in their pattern or colour or shape, and are valuable in their own right as interesting and beautiful stones. However, they do get smaller after each stage. This tiny stone from Gemstone Beach is an example of the exquisite character that a small stone can have:

The stone is 2 cms long and 1.5 cms wide and 0.5 cm thick (see photo at bottom of page for comparison with some other Stones of the Day). It might be a jasper, though sometimes we too often identify a stone as jasper simply because of the dark red colour when other kinds of stones, such as quartzites, can also be that colour due to the presence of iron oxides. The stone has been tumbled in 400 grit, then 600 grit. After 17 days in tin oxide tumble polish, it was burnished for nine days in borax. The extra tumble in 600 grit is an experiment I have been conducting recently for especially jaspers and stones consisting of more than one mineral, to try to get the whole pre-polish surface as smooth as possible. I have also been lengthening the times of each stage to see if this improves the final product. This tiny stone has polished very well.

Other side of Stone #19.

What attracted my eye to this small stone on the beach was the light red, almost pink, splash of colour at one end. Polishing has clarified the whole stone and revealed the clouds of colour throughout it. What has also become apparent is a small stress offset (faultline) that has been filled in by some kind of silica (could be quartz):

The small faultline in Stone #19.

The small faultline in Stone #19.

The “small stones” of an earlier Post https://tumblestoneblog.wordpress.com/2019/06/21/little-things-the-value-of-small-stones.

Stone #19 compared for size to other Stones of the Day.

The Index to the January 2022 Stone of the Day Series is here.

This small orbicular hematite jasper was found on Gemstone Beach early in 2021. I have found a limited number of other such stones there and at Kakanui, though this might be the biggest. It is still quite small, being 3.5 cms long by 3 cms wide by 1.5 cms deep. As well as generally being small stones, orbicular jaspers often have cracks and pits in them so that I have not yet been able to produce a fully smooth polished one. This is one of the best, with only one very thin crack and a three tiny pits marring its smoothness.

#4

Such stones often get a little more time in 400 grit from me, often repeating the stage, before going on to be polished, to try to minimise the cracks and holes. As I noted in a previous Post about a similar stone, Mindat states that orbicular jasper is “a highly silicified rhyolite or tuff that has quartz and feldspar crystallized into radial aggregates of needle-like crystals forming orbicular (spherical) structures”. If the orbs are red, we tend to call it “poppy jasper”.

The other side of Stone #4.

A very similar type of stone is “brecciated jasper” – see the “H is for Hematite Jasper ” entry in this Post for information about this small brecciated jasper I found on Gemstone Beach in February 2021 (compared below with a photo of another small orbicular jasper I found on Gemstone Beach on 22 June 2021):

Brecciated hematite jasper.

Another small orbicular jasper found on Gemstone Beach, 22 June 2021

Hematite is an iron oxide compound widely found in rocks and soils. It occurs naturally in a variety of colours – black to silver-gray, brown to reddish-brown, and red. It is the silvery gray and black that are most noticeable in Stone #4.

Stone of the Day #5 is here. The Index to the January 2022 Stone of the Day Series is here.

J is for (Picture) Jasper

K is for Kai Iwi Beach Stone

L is for Leithfield Beach petrified wood

M is for Muscovite Mica from Joyce Bay

N is for November in the Calendar

The following are my Posts for “O” and “P” in the alphabetical series of a Facebook Group I belong to, “New Zealand Lapidary, Rocks, Minerals, Fossils”. The first Posts in this Series can be found here.

“O” is for “Opaque Orepuki Orbicular Jasper” – This small (thumb-nail sized) tumble-polished orbicular hematite jasper was found on Gemstone Beach, just a kilometre west of the small Southland town of Orepuki.

A small orbicular hematite jasper from Gemstone Beach, Orepuki.

Jasper is an “opaque” rock. Opaqueness is one of the three main ways of classifying how light passes through a stone or rock. “Transparent” means light passes through easily (e.g., clear quartz); “translucent” means only limited light is able to pass through the stone, so that an object held behind it would look fuzzy; “opaque” means light does not pass through the stone at all. Jasper is an opaque form of chalcedony, a cryptocrystalline form of silica. Chalcedony itself is usually described as semi-transparent or translucent. The incorporation of minerals, such as iron oxides, provides jasper with its opaque nature. “Orbicular” jasper is a variety of jasper which contains orbs or spherical features. Mindat states it is “a highly silicified rhyolite or tuff that has quartz and feldspar crystallized into radial aggregates of needle-like crystals forming orbicular (spherical) structures”. If the orbs are red, we tend to call it “poppy jasper”. One type of orbicular jasper is “ocean jasper”, a trademarked name for a multi-coloured stone from Madagascar. Sometimes it can be difficult to distinguish between orbicular and some forms of brecciated jasper.

Page 72 of A.B. Busbey, R.C. Coenraads, D. Root and P. Willis, 2013, “Rocks and Fossils”.

Part of page 72 of A.B. Busbey, R.C. Coenraads, D. Root and P. Willis, 2013, “Rocks and Fossils”.

Page 122 of P. Polk (2016), “Collecting Rocks, Gems and Minerals: Identification, Values, Lapidary Uses”.

Part of page 122 of P. Polk (2016), “Collecting Rocks, Gems and Minerals: Identification, Values, Lapidary Uses”.

Www.mindat.org/min-27171.html

Ocean jasper. https://www.entertheearth.com/the-geology-varieties-and-history-of-ocean-jasper-part-one/?fbclid=IwAR3sBTOMAxOzoMR1I5G76-1Yujb0ZZqpdR4PTCsqWum0o4XGYOLtHVPOVQY

A similar small jasper stone from Gemstone Beach, could be brecciated rather than orbicular, difficult to tell clearly.

My stone was found on Gemstone Beach near Orepuki, which Wikipedia describes as “a small country township on the coast of Te Waewae Bay, some 20 minutes from Riverton, 15 minutes from Tuatapere and 50 minutes from Invercargill”. Once a thriving settlement of 3000 people, with gold mining, oil shale, and flax being big industries, today about 60 people live there, with the tavern and café being the only two town businesses (http://www.stuff.co.nz/…/orepuki-much-more-than-just-a…). The Wikipedia entry on Orepuki mentions nearby Gemstone Beach, even noting that “this wild beach contains semi-precious gemstones such as… orbicular jasper” (https://en.wikipedia.org/wiki/Orepuki). The photo below of the sweep of Te Waewae Bay, looking west past Gemstone Beach, was taken at the spot marked with a red X on the satellite map, on the eastern outskirts of Orepuki.

Gemstone Beach scene.

Looking west along the sweep of Te Waewae Bay. Photo taken from eastern outskirts of Orepuki, with Gemstone Beach being 1 to 2 kms from this point. The site from which the photo was taken is marked on the bottom left of the next photo.

Orepuki and Gemstone Beach on Google Maps http://www.google.co.nz/…/@-46.2811355…/data=!3m1!1e3. Red X at lower left marks spot from which previous photo was taken.

Page on oil shale mining at Orepuki on 19th century – page 19 of Heritage Trail booklet.

Page on Gemstone Beach area – page 25 of Heritage Trail booklet.

Booklet I bought from Riverton/Aparima Museum Shop.

“P” is for “Planet in a Pebble” – This small polished grey stone is from Gemstone Beach. Like a handful of other stones I have found, it is possible to imagine that you are looking down on a planet from space, with lots of stuff going on in the atmosphere or on the liquid surface.

“The Planet in a Pebble” is also the title of a book published in 2010 by the Polish geologist Jan Zalasiewicz, sub-titled “A Journey into Earth’s Deep History”. In this fascinating and engaging book, he tells the story of a pebble’s history, stretching back billions of years. In Chapter One, “Stardust”, he points out how, at the atomic level, a pebble and a person share the same kind of atoms – we are kin. And a pebble is a microcosm of the Universe, made up of that which goes back to the singularity of the beginning of everything. Zalasiewicz writes on page 7, “The pebble, in this respect, is as deep a mystery as is everything else in the Universe. How did the matter of that pebble, and of the…hills it was torn from, and of the world it sits atop – and of the Solar System and of the Milky Way, and of countless galaxies near and far – manage to unpack itself from a point: a ‘singularity’, as many think, of no size at all?” As I mentioned in a blog post I wrote five years ago, a pebble is made of stardust and in it we encounter not only our selves but also the depths of the Earth and the heights of the heavens. Looking down is a way of looking up. Looking into a stone is also to glance across deep dark space and even time. In a stone we make contact with that which is closest to home as well as that which is furthest away. The photos of the stone below include colourful experimental ones, playing around with Picasa software.

See here for the next Post in this Series, and here for the Series Index.