Thirty Gemstone Beach Pebbles for Doug: Part Five – Stones 24 to 30

I was recently interviewed about stone collecting by Doug, a journalist for Whanganui’s River City Press. Afterwards he asked to buy some of my polished stones so I picked out 30 Gemstone Beach stones for him. When he took my photo for the article, Doug got me to hold a printout of the 30 stones.

Southland’s Gemstone Beach, located near the small town of Orepuki, has a great diversity of colourful and interesting stones. Their value lies NOT in being precious gemstones (because they are not!). But their value lies in the fascinating features and patterns within each stone, often only fully revealed in close-up photos. Tumble polishing the stones applies a permanent clarity to their surface so that their inherent visual art is always on display. My Post “March 2019 Stone Collecting Trip to Southern New Zealand – Gemstone Beach, from the Car Park to the Waimeamea River Mouth” describes the kilometre long stretch of beach that I walk in order to find these stones. I usually spend around three hours at a time there on each visit. In March 2019, in five visits, I collected about 18 kilograms of stones to take home to Whanganui to polish. These days, I pick up less stones, being much more selective, but I always find fascinating ones and often something new and unexpected (see the end of this Post, below).

To continue with Doug’s 30 stones…

Part One in this Series, covering Stones #1 to #5, is here. Part Two describes Stones #6 to #11; Part Three is about Stones #12 to #17; and Part Four features Stones #18 to #23. The final seven stones, the smallest, are now presented.

Stone #24 is a very strange stone and a mystery to me:

It looks like there is a lot of quartz in the stone but the top part of it has a significantly different appearance to the lower part. There is an interesting boundary band between the two as well. The top part has some different-hued patches in it but what catches the eye are the thin veins of a very dark mineral running across it. When I saw this on the beach, it immediately stood out as unusual. I wondered if it was a fossil of some kind, or a shell embedded in a stone. The photos show that it is all one stone, but with intriguing markings.

Stone #25 is the same type as Stone #9 (in Part Two), probably a quartzite with a fine lace-like tracery of mineral through it:

However, whereas the tracery is yellow in Stone #9, it is green in Stone #25. Patterns like these always catch my eye on the beach. The green is caused by epidote, a mineral we have seen before in Doug’s stones.

Stone #26 consists of small rock fragments (called “clasts” by geologists) from a variety of sources, making it “polymictic” in contrast to Stone #6 (in Part Two) and Stone #19 (in Part Four) which are “monomictic” (their clasts come from only one source):

However, is Stone #26 a breccia or a conglomerate? As I have previously noted, in a “breccia” stone, the clasts have not travelled far before being cemented together so they are angular and sharp. In a “conglomerate”, the clasts have undergone some rounding from the travel they have experienced, usually from water, prior to being cemented together. There is maybe some rounding of some of the fragments in Stone #26 but most fragments are angular, so it’s probably ok to call it a breccia. However, some stones are a mix, not fitting clearly into either category. It’s not unusual to find stones like that – the neat general categories of geologists are very useful but individual stones do not always line up precisely with them.

Stone #27 is a white quartzite:

Such quartzites appear to have thick “clouds” of intense mineral within them. There are some similarities to what I called a “canyoned” green quartzite I found on Gemstone Beach in March 2023. Another similar stone is the second one in this Post, a very dark green quartzite I found in March this year. On side B of Stone #27, you can see some holes that have not been smoothed out by the tumble polishing. They can ruin the look and the feel of a polished stone. However, to get rid of the holes in such a small stone would wear it away to practically nothing, and the stone is too interesting to lose.

Stone #28 is the kind of stone as Stone #21 (Part Four), a quartzite full of the green mineral epidote:

There is a prominent vein of translucent or transparent quartz running through side A of this stone. Such a “vein” is an infilled crack. When rock comes under pressure and stress, it fractures, and cracks of different sizes open up. This allows hydrothermal fluids, carrying dissolved minerals, to enter the gaps in the rock. Over time, the dissolved minerals precipitate out of the hot water. Crystals, such as quartz, grow within the cracks and fill them. Often, as the stresses on the rock change their orientation over time, veins can crosscut and even overlie each other.

I often discover that the smallest stones I pick up on Gemstone Beach are the most fascinating ones. When wet on the beach, they can catch my eye despite their small size. But their full beauty can’t be appreciated until close-up photos are viewed. Stone #29 is such a stone – it turns out to consist of a patchwork of colours and veins:

It’s a stone that has been subject to a lot of tectonic pressures and its veins have been flooded with different minerals at different times, contributing to its delightful patchwork.

Stone #30 is the smallest of Doug’s stones but to me it is the most gorgeous:

Like a lot of the stones I find and polish, it is mainly a mystery. I don’t know exactly what type of rock it is, though it will be one of the volcanics. It is amygdaloidal, like Stone #23 (Part Four) – a stone with many tiny vesicles (gas holes) that have been infilled with minerals. But I don’t know what these minerals are. When I picked up this stone from the beach and looked at it closely, I knew it would be interesting. But the photos made me gasp as they revealed a whole ‘nother world of tiny detailed beauty.

The rest of Doug’s 30 stones feature as follows: Stone #1 to #5 = Part One; Stones #6 to #11 = Part Two; Stones #12 to #17 = Part Three; Stones #18 to #23 = Part Four.

**********

Gemstone Beach has provided me with many fascinating discoveries – photos of six of my most valued are below. The first is a fossil coral, the only one I know to have been found on the south coast (and it’s likely to be very rare even for New Zealand). I glimpsed it on the beach in June 2020. Such a stone is the official State stone of Michigan where it is known as a petoskey stone. See “C is for (Fossil) Coral”. The second stone below is a bright pink thulite I found in September 2024. Thulite is the national gemstone of Norway where it was first discovered in 1820. I can sometimes find one or two thulites on a visit to Gemstone Beach, but not always, and the quality of their pink varies. More information on this mineral can be found in “January 2022, Stone of the Day #5 – A Little Pinky”.

The third stone below is probably chromium in diopside in hydrogrossular garnet, found in March 2024 (“chromium in diopside” is the intense green colour) – I used it for the month of January in the 2025 TumbleStone Calendar. I found the fourth stone, a poppy (orbicular) jasper, in September 2024. GeologyScience states: “The distinctive 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.” For a similar poppy jasper plus more information on orbicular jasper, see “O is for Opaque Orepuki Orbicular Jasper”.

The fifth stone below is a very rare white orbicular jasper I found in March 2025 – see “March 2025 Stone Collecting Trip – Part 25, A Small White Orbicular Jasper From Gemstone Beach, Friday 28 March”. The final stone below is a small jasper with chalcedony veins. It’s the size of my thumbnail. On the beach, it looked like a red jasper with some white patches plus some tiny veins. The veins seemed to have some bright white in them. The photos revealed some fascinating details – see “Southern Sojourn 2023(12): Surprises and Revelations, Gemstone Beach, Friday 10 February”.