In this Series, I present 30 recently polished stones from Gemstone Beach/Te Waewae Bay. They illustrate the great diversity and beauty of the pretty stones of this beach, as well as some of the challenges a tumble polisher faces to obtain a completely smooth and well-polished stone (if that’s their aim). These 30 stones were selected from the smaller stones from batches tumbled in two 3lb barrels. Part 1 described Stones 1 to 5. The next five stones, featured here, are slightly smaller than the first five.
Stone 6 is a mix of colours and shapes. On the beach, the bright sweep of opaque white on Side A caught my eye, then the green (most likely epidote), then, upon closer inspection, the intriguing veins.
This is a good example of a small stone that reveals more and more as you look closer at it. Though tiny holes are also among the things revealed.
Stone 7 is an example of a stone that from a distance appears to have a simple makeup – some light-coloured patches and some slightly darker patches.
But closer inspection reveals an intricate mosaic of what could be tiny crystals in an irregular latticework pattern. It’s an amazing and beautiful stone, but I don’t know what kind it is. A few tiny scratches can also be seen.
Stone 8 has contrasting sides. It’s a type of quartz, I call it a sugary quartz because of the small granular-like crystals that make it up. Side A has a brown hue, Side B has a whiter hue.
The difference in colour will be due to variation in the presence of a brown mineral, most likely iron oxide. Stones of this “sugary” composition can be hard to get completely smooth through the tumbling process, with tiny grains coming loose from the surface. However, I like how they look and have had success with a number of them.
A small black and white volcanic stone, Stone 9 is full of amazing tiny white crystals.
The crystals are elongated and appear to float throughout the black material. Generally speaking, the longer it takes for volcanic rock to cool, the larger the crystals in it will grow, having longer time to form. In this Post on igneous stones from Gemstone Beach, Stones W43 to W56 illustrate the diversity of white crystal shapes and sizes that can be found.
Stone 10 looks like a pale-coloured mudstone, but it has some interesting dark veins or lines in it. These are likely to be dendrites, thin branching lines of crystals, often of some variety of manganese oxide (or iron), that grow over the surface of a stone. They are found in cracks or along bedding planes. The word “dendrite” is from the Greek word for “tree”, referring to its branching appearance.
Mindat has some good photos of dendrites and Sandatlas has a technical explanation of their growth. Thornton provides some NZ examples of dendrites in agates in her book “Gemstones” (page 15 here). Dendrites are often given as examples of “pseudofossils”, natural objects that may be mistaken for fossils of, for example, a plant leaf.
Part 3 in this Series examines Stones 11 to 15.
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