What kind of rock is this?

Asked May 13, 2018, 9:21 AM EDT

My dad collects a lot of random rocks as he is an avid gardener. Recently he found a rock which has some small metallic looking pieces in it. What do you think it could be? We live in South Africa if that helps. Thanks!

Outside United States rocks and minerals rock identification geology

1 Response

Nice specimen! From the images, it appears to be quartz with inclusions. The crystal habit of the inclusions looks flakey like muscovite mica. There is a lovely golden muscovite https://en.wikipedia.org/wiki/Muscovite. It could also be any number of metallic minerals with pyrite being a possibility. Igneous Intrusives include granitic rocks which cool slowly, giving minerals a chance to crystallize.

I'm not familiar with South Africa geology but did find this paper which talks about granitic intrusions. http://www.the-eis.com/data/literature/Geology%20and%20alteration_mineralization%20of%20the%20Brandb...
The rock also indicates a second life as a river cobble. I suggest for further identification, take it to a local geologist. Great find!!