The Introduction to this Calendar can be found here. The Calendar features beach stones collected during my two South Island fossicking trips in 2024. The month of January features Gemstone Beach, on the south coast of Southland, along with four stones I found there in 2024. February takes us 140 kilometres west to Slope Point, in the Catlins District, also in Southland.
Note that the stones in the Calendar were photographed in the rough and while wet, being held in my hand in bright sunlight. So this is how I first saw them on the beach. However, the photos often reveal details not initially grasped. Three of the eight stones below are labelled “unknown”. My identifications for others include tentative suggestions – my research and understanding are ongoing.
JANUARY – GEMSTONE BEACH
January’s scene of Gemstone Beach (below, left) was photographed on 6 March 2024. The previous day had been quite stormy, and snow appeared on the tops of the mountains in the distance. I took the photo of people looking for stones in front of the carpark just as I was leaving the beach after a three hour fossick. The TumbleStone Blog Post for that day was entitled “Another Post-Storm Fossick Finding Treasures on Gemstone Beach”.
The first stone that appears in January in the Calendar, at the top left of the page, is an “unknown” one. I found it on 12 March during a fossick that included encounters and conversations with a number of people on Gemstone Beach – see “With Claire and Brett on Gemstone Beach”.
I really like the contrasting light and dark areas in this stone as well as, unusually, the diffuse nature of the patterning. This is unusual in that I generally seek out stones with well-defined tiny details. The lighter material in it could be quartz or quartz-derived, with maybe epidote providing a tiny tinge of green here and there. I don’t know what the black mineral is. It’s always nice to be able to identify a stone but the lack of an identification does not detract from its attractiveness.
January’s second stone, top centre of the page, was an exciting find. It was also found in March this year, just a couple of days before Stone 1 – see “Sunday Afternoon Fossick, Gemstone Beach and Te Waewae Bay”. I was immediately attracted by the bright intense green within the stone.
Closer inspection also reveals some intriguing white “swirls” in the lower part of the stone. I posted a photo of a similar find in the Facebook Group “New Zealand Lapidary, Rocks, Minerals, Fossils”, asking if anyone could identify it. Someone from Nelson responded – rocks in the Southland area and Nelson area are often similar as they were originally connected prior to the Alpine Fault tearing them apart. He commented that it looked a lot like the chromium in diopside in semi-nephrite he knew from his local region. Also called “chrome diopside”, the mineral is a vibrant green variety of diopside coloured by chromium – see Mindat here and here. I have no experience of semi-nephrite, though it is mentioned as present on Gemstone Beach. I have tended to think of semi-nephrite as dark in colour and initially wondered whether the white part of this stone might actually be hydrogrossular garnet. However, I have recently come to understand that nephrite and semi-nephrite can be white – here are three examples of spots of chrome diopside in nephrite, carvings by Wayne Costar that he had posted on Instagram. The second of these has significant white in it.
Another example of chrome diopside in white nephrite can be found here. Nephrite is not found on Gemstone Beach but semi-nephrite is sometimes mentioned as present there. This example of a Gemstone Beach semi-nephrite is a light green colour. Semi-nephrite, as one source puts it, is a low-grade form of nephrite. In other words, it is a rock that is on its way to becoming nephrite but is not quite there in terms of mineral structure. Semi-nephrite is dominated by large tremolite mineral crystals, which occur within a mass of smaller crystals. These differing crystal sizes create a structural weakness that contrasts with high-grade nephrite, which is very strong. It is not beyond the realms of possibility that January’s Stone 2 is semi-nephrite.
January’s third stone is a poppy jasper, also known as orbicular jasper. The size of the orbs in poppy jaspers range from tiny to large – this stone has orbs of the larger variety (July’s poppy jasper has much smaller orbs). You can also see hematite, a grey metallic mineral, in the stone – its presence always seems to intensify jasper’s deep red colours.
One of the stones I found on the day that the photo of the month’s beach scene was taken is the fourth stone for January – the jasper on the lower right of the page. See the Blog Post “Another Post-Storm Fossick Finding Treasures on Gemstone Beach”. I found the stone in an area I don’t often visit, just to the left (eastwards) of the carpark, on the other side of The Steam With No Name. I remember it was amazingly smooth and its clear vein caught my eye along with the patches of metallic hematite and the flowing lines of contrasting dark and light.
The stone appears to have come under tectonic stress, causing some brecciation and creating openings for the clear silica to enter. I have now tumble-polished it and it is outstanding, looking very similar but bright and clear.
FEBRUARY – SLOPE POINT
February’s beach is at the head of a small bay, just under two kilometres east of Slope Point, the southernmost tip of the South Island. I visited there on 2 March 2024, accompanied by Chrissy Lampitt who can be seen in the beach photo (below, left). The TumbleStone Blog Post for that day was entitled simply “A Sunny Slope Point Fossick”. A more detailed introduction to the beach is provided in a Post about a fossick there in March 2023, “Journeying to a Slope Point Beach”.
The first stone that appears in February in the 2025 Calendar, at the top left of the page, is an “unknown” one. It is primarily black, and appears to have some light-coloured orbs in it.
It was found on this beach on 13 March 2024, along with this month’s Stone 3. Another type of orbed stone, spherical or chrysanthemum rhyolite, can also be found here – see this Post for examples, and August’s Stone 4.
20 November: Stone 2 has just been tumble polished, and I’m not sure it has been improved, except for now being permanently shiny. Some orbs have lost their centre dot, though some other light-coloured features have made their appearance.
February’s Stone 2 is a breccia, found on 20 September. Breccia of various kinds are present on this beach.
As I note in a previous Post, in “breccia”, the fragments (or “clasts”) that make up the stone have not travelled far before being cemented together and so are angular and sharp. In a “conglomerate”, the fragments have undergone some rounding from the travel they have experienced, usually from water, prior to being cemented together. Sometimes, a brecciated stone is caused when massive stresses on a rock tears fragments from it which are then cemented in a matrix – this is often known as “tectonic” breccia. Other times, “sedimentary” breccia occurs, when fragments from different stones end up cemented together in a fine-grained matrix. A third main type is “igneous” breccia, where the clasts consist of pyroclastic debris ejected by a volcanic blast or pyroclastic flow. It is known that some Slope Point stones have arisen from Jurassic Era volcanic activity and debris flows, so I suspect Stone 2 is volcanic breccia. It is also “polymictic”, a breccia where the fragments or clasts come from more than one rock type.
Stone 3 is my most prized find from my four fossicks on this Slope Point beach this year. It is my first piece of petrified fern. In my Post on my 13 March visit, “Second Slope Point Fossick”, I described its discovery as follows: “I was sitting on a rock, resting before leaving the beach to tackle the steep climb back to my car, (when) the edge of a dry stone with squiggles in it caught my eye.”
In her booklet, “Gemstones” Jocelyn Thornton writes on the pebbles to be found at Slope Point (page 35): “The prize is petrified punga, found as black nodules barely showing the eyed grain of the fern.” The grain in this stone is much clearer. It is currently in the tumble polisher.
20 November: Stone 3 is now polished. There are two or three small rough areas on the surface but I didn’t want to tumble it longer to fix those as it would just make the end product smaller.
The surface of the stone has changed quite a bit due to the tumbling. For example, one area of the stone has an oval feature with a squiggly oval in the centre. The tumbling has removed the squiggly centre:
Stones with detailed features in them are at risk of such changes in tumble polishing.
February’s Stone 4 is another “unknown”, found on 2 March.
Its light colour caught my eye initially, then I noticed that it appears to contain a range of different crystals.
March (Seadown Beach, Kakanui) and April (Gemstone Beach) in the Calendar are featured in the next Post. These 2025 Calendars are for sale, with postage within New Zealand included, for $30 non-rural, $35 rural. Contact me at john.tumblestone@gmail.com.
When I spotted your second January stone I was struck by how much the white and green colours resembled a necklace I have that I was told was a type of nephrite with chromium diopside from the Nelson region. The green in my necklace is also very vivid.
Many thanks for your comment. It reinforces that I am on the right track with this ID.