This afternoon, I had my last fossick on Gemstone Beach for this trip, and I found a very unusual little stone. Chrissy and I were fortunate that the rain showers stopped just before we started. However, we had to brave a cool wind and 13 to 14 degrees throughout the more than three hours we were there. But there were good pickings.
We found quite a few hydrogrossular garnets and trace fossils, a few nice jaspers, and a diversity of other interesting stones. I collected a few more stones than usual, given that I am about to head back home. A big “Thank-you” to Chrissy for her companionship and enthusiasm during a number of my fossicks this trip, and for keeping me safe on the beach. Below are 11 of my finds today.
The “hero” of today’s finds is this small stone – its full glory is revealed by the close-up photos. It’s like a poppy jasper but the tiny orbs are white, not red:
This is a type of orbicular jasper. On Mindat’s photo gallery of 57 examples of orbicular jasper, there are none exactly the same but there are a handful of stones with white orbs, three of them with tiny ones:
Strekeisen’s Post on “Ocean Jasper” (orbicular jasper from Madagascar) also includes an example with a couple of patches of white orbs (photo below, far left). Stones of Ocean Jasper for sale also include white-orbed ones (centre and far right photos below).
Mindat states that the orbs originate when “the material forms in radial aggregates where small ‘seed’ crystals of quartz or feldspar create the rounded shapes”. 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.” GeologyScience also notes that the pattern of orbs can consist of concentric circles, spherical shapes, or irregular spots. The orbicular patterns vary widely in size, colour, and arrangement.
The next small stone is also partly an orbicular jasper, the red colour of its orbs leading to its name of “poppy” jasper:
Another interesting jasper, maybe kind of orbicular, maybe brecciated??
Another red stone, but this one turns out to be a polymictic breccia, probably of sedimentary origin:
As I have mentioned in previous Posts, in a “breccia”, the fragments (or “clasts”) that make up the stone have not travelled far before being cemented together and so are angular and sharp, as in this stone. In a “conglomerate”, the fragments have undergone some rounding from the travel they have experienced, usually from water, prior to being cemented together. For some information on brecciated stones and Gemstone Beach, see “January 2022, Stone of the Day #2 – Breccia and the Giant Landslides of Fiordland”. ThoughtCo has a good article on breccia. 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 – the stone above is probably of this type. A third main type is “igneous” breccia, for example, made up of tiny bits that have come from a volcanic eruption A breccia where the fragments represent more than one rock type is called “polymictic” while one where the fragments come from just one rock type is termed “monomictic” (University of Auckland Geology).
The next stone has a lot of green epidote in it and a smattering of other material all mixed in:
A stone with more subtle characteristics and colour, a green tinge provided by scatterings of epidote:
Two of the hydrogrossular garnets I found today:
I wonder whether the lighter material in the next stone could be hydrogrossular garnet, but I don’t really know:
A slightly-raised trace fossil in a pale argillite stone:
Finally, a yellow stone with a lot of quartz in it:
This was my sixteenth fossick on Gemstone Beach this month. Each time, I found some amazing stones, some well-known to me, like hydrogrossular garnets, poppy jaspers and trace fossils, but also some completely new. I also met a number of interesting people, and dogs. But time to head for home.
On my way home, I stopped off to visit Kakanui’s Seadown Beach again – see Part 26. An Index to this Series is here.
