The GemHunter

Professor Hausel's Guide to Finding Gemstones, Diamonds, Gold, Rocks & Minerals 

Unusual Rocks

One of many unusual rock types known as spinifex-textured komatiite

Photo to the left is from the Hannas Lake Serpentinites in Western Australia. This is an ultramafic spinifex komatiite. If you find any rocks like this one, you may be near a gold, nickel or chromite deposit.
These rocks are typically found in greenstone belts around the world. 

Another uncommon rock is kimberlite. Kimberlite was named after the Kimberley Region of South Africa. It has also been found in North America in Canada, Colorado, Wyoming, Montana, Michigan, New York, Kansas, Kentucky and Tennessee.