Hey I found your blog recently and from one aspiring geologist to someone who clearly loves rocks, are there any cool facts or things about rocks that you’re just dying to share. Heres mine: silica gel itself isn’t poisonous but the chemical they use to make sure you know its not dry is! We actually eat silica all the time in our salts and sugars, but since we don’t gain anything from it- it leaves the body like nothing. Sorry for the long paragraph but I love ur art and ur rocks! Have good day!
Here is a Cool Rock Fact that I have always wanted to talk about because I find it absolutely fascinating, and also because I have a burning need to dispel some misinformation I’ve seen people spreading around on my rock posts. I want to apologize in advance for this unreasonably long essay about Cool Rocks that no one wants to read, but YOU DID ASK.
When I made my very first rock post I included a picture of my tiger iron, and a bunch of people were Very Upset and Concerned because tiger iron contains tiger’s eye, and isn’t tiger’s eye made of asbestos?
And that’s a huge misconception! Tiger’s eye is not asbestos, and it’s a totally safe rock to handle. What’s ACTUALLY going on with tiger’s eye is way more interesting! AND I WILL TELL EVERYONE ABOUT IT RIGHT NOW IMMEDIATELY!!
This is a big chunk of raw, unpolished tiger’s eye! It’s a type of quartz with a really incredibly cool crystal structure. It’s made up of tiny fibers, and these thin, parallel threads give it its famous chatoyancy: that line of light that shines across it when you move it around.
Quartz doesn’t grow in tiny, shiny fibers. Asbestos does. But the big chunk of rock I’m holding in my hands right now is quartz, not asbestos, so what gives? (I say facetiously, about to go into a massive infodump about exactly what gives.)
Tiger’s eye is a pseudomorph. It’s a rock that started as one thing, but became another, but still LOOKS like the first thing. Everybody knows how fossils work, right? The organic material is slowly replaced by minerals, which retain its original shape! Petrified wood still takes the shape of the tree, and even retains its rings, but it’s made of silica, or opal, or aragonite… The exact same process is what makes tiger’s eye!
Long ago, this was a blue rock called crocidolite. It was a form of asbestos and it grew how asbestos grows, in tiny fibers. Then over time, a microscopic layer of quartz started coating these fibers. In the blue and green versions of tiger’s eye, (often sold as hawk’s eye and cat’s eye) the fibers of asbestos are still trapped inside, but they’re tightly bound up in the quartz. They can’t escape into the air and cause you any harm, but their presence gives the rock its color!
In yellow-orange tiger’s eye, there’s little to no asbestos left in there. It’s all deteriorated via oxidization (with the help of certain chemicals in the environment to kickstart the reaction, oxygen got in there and changed its chemical structure which made it fall apart, like how iron rusts). The space left behind got filled with more quartz, and some other stuff like limonite. The iron in limonite gives tiger’s eye quartz its golden color!
Anyway, I told you that fact so I could tell you this much cooler one.
Here’s the interesting part, all that’s just a theory. It’s the most widely accepted theory, but science is still debating exactly what’s up with tiger’s eye and how it forms. It’s probably a pseudomorph, but it doesn’t look at all like you’d expect pseudomorphic quartz to look when you examine it microscopically, so there’s definitely some other factor involved in its formation that we haven’t figured out yet!
And the scientific community gets into heated debates about this.
It’s possible that instead of being replaced by quartz, the crocidolite is undergoing some chemical reaction that turns it into quartz. It’s possible that the quartz actually grew alongside the crocidolite to begin with, making it not a pseudomorph at all! We think maybe the crystals cracking and deforming under geological stress might be involved? It’s possible the chemical compositions of quartz and of crocidolite interact with each other in ways we don’t understand yet, and that’s why it looks weird microscopically? What we do know is that it looks Really Weird Microscopically, You Guys. People yell at each other in geology forums over this. It’s amazing.
So that’s how you get a rock that appears to have the crystal structure of asbestos, but is actually just regular old safe to handle quartz! Since it’s (maybe) a pseudomorph, I guess it would be more accurate to call this stuff Quartz After Crocidolite, but that’s not as marketable a name. Pseudomorphs are super cool, and there are all kinds of rocks that can form in weird crystal structures because of them! One of my favorites is the super colorful ammolite, which is Aragonite After Ammonite Fossil.
But I digress, is tiger’s eye made of asbestos, and is it dangerous? The answer is that it’s sort of made of asbestos, but also kind of not really, and it’s no more dangerous than regular quartz. There’s a LOT of misinformation out there about this very cool rock, because the word “asbestos” is scary and the science behind why it’s actually totally safe is complicated. And that makes my rock loving heart very sad.
But, uh… that’s a Cool Rock Fact I’ve always wanted to talk about. Thanks for asking!
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