![]() ![]() It’s superficially similar to diorite, which can be found on the margins of continents and washes up with some regularity on beaches.īut unless you’re headed down to Mexico and have access to a mine, self-collection isn’t something that you’ll be able to do. Igneous rocks can be like that at times, where a unique combination of minerals just doesn’t show up anywhere else. It turns out that dalmatian stone is actually comprised of albite (a plagioclase feldspar mineral), and quartz, and the black bits are a mineral with the unwieldy name of arfvedsonite.Īs far as I can tell, the variety that’s sold as dalmatian stone is found in mines in Chihuahua, Mexico, and not anywhere else. The folks over at actually sent in a few samples for lab analysis. Most people dropped it there, I believe.īut, as the old saying goes, “Everybody has a theory until someone ponies up a few bucks for X-ray diffraction.” A Definitive AnswerĪs it turns out, someone actually did that. ![]() This makes sense to some degree, tourmaline is very similar to quartz in hardness. The most common theory I saw was that it was a mixture of quartz and schorl. That ruled out any kind of cryptocrystalline quartz in my book. I’d tried to make an arrowhead from a leftover bit of slab a few years back through knapping and it just kind of… broke. It also didn’t display a conchoidal fracture. I read more than once that it was a jasper with hematite inclusions, which seemed kind of odd considering the colors of most jasper are already created by iron oxides. Some people were clearly just throwing things at the wall to see if they stuck. The good stuff comes from Mexico”Īs I poked around, I realized that not many people seemed to have any idea of what it was. Go poke around near continental shelves to find it. I had actually assumed that would be the end of it for this article: “It’s not a jasper, it’s just diorite. It was obviously different than the stuff washing up on Santa Barbara beaches, but not by much.ĭiorite is comprised of plagioclase feldspar, biotite, and hornblende with a smattering of other minerals found on occasion. Diorite is a coarse-grained stone with a composition that’s the same as the finer-grained andesite. Indeed, when chunks wash up on the beaches around where I grew up diorite was often called dalmatian stone. I had just assumed it was a diorite variant. It was still uniform in hardness, if a bit soft. Jaspers tend to have a certain look to the rough pieces and are a bit of a specialty for me. To my eyes, it’s never quite looked like a jasper but I never thought about it too much since I only ever cut a few pieces as custom cabochons when folks wanted it. Think about rainforest jasper for a moment, it’s just a really nice rhyolite that cuts and polishes well, but you simply can’t convince many people it’s not actually a jasper. A lot of materials like this end up being called jasper for some reason. It polishes well, cuts without chipping, and is generally pleasant to work with as a lapidary material.
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