SciShow Rocks Box: Tiger Eye Chunk

Formula: SiO2 Mohs Hardness Scale: 6.5-7 The shimmery, golden-brown mineral in your hands is called tiger’s eye, and it certainly is a looker. That warm glow comes from thin bands of needle-like inclusions inside a quartz core. But for more than a hundred years, geologists were totally wrong about what those needles really were! Back in the late 1800s, a geologist looked at tiger’s eye and a form of asbestos called crocidolite and decided that the tiger’s eye probably was formed when the threads of asbestos were chemically replaced by pure quartz. But the funny thing is, it took over a hundred years for anyone to follow up on the whole idea. It turns out it was wrong, because modern high-res imaging has shown us that the asbestos is still in there! Don’t worry, tiger’s eye is still totally safe to handle, so you can admire these shimmery rocks and the geology behind them all you want.