What rock is this?

Asked February 27, 2016, 10:14 AM EST

I found this rock recently. It looks like a normal quartz to me but the whole rocks are filled with tiny brown crystals. Can anyone tell me what is this?

New York

1 Response

The brown color looks like iron which is common in many rocks. Those may or may not be quartz crystals - many minerals form 3-D shapes and it almost looks like the less-colored crystals grew from a solution where some solutes moved and grew the crystal but the iron was left behind. I think your best bet would be getting a mineralogy guide from a library and working through an identification key. Many minerals can be identified by relative hardness (scratch tests). I ran this by some folks at the New York Geologic Survey and they agreed, likely to be iron in the orange/brown, but both parts need to be worked through a key with the rock in hand to identify for sure.