You are here:

Geology/Rock with sparkles in it


I bought a bag of polished stones at a second hand store. In the collection there is a grayish brown stone that when you turn it in the light reflects purple , blue , green flecks inside. Just wondering if you know what it might be. Thanks

Hi Pat,
Without a pic it's pretty much impossible to tell what you have with any certainty.  But your description of light reflecting off different colored flecks makes me suspect you have a stone called "Goldstone". It's considered a gemstone and you often find it in a group of tumbled stones.  It's artificial, and is a glass made in a special oxygen reducing atmosphere.  It was rumored to be made by Italian monks but there is no hard evidence for that.  There is documentation that a family in Venice #Miotti# made the first goldstone in the 17th century.

Here's a picture of some typical goldstone;

It can be any color but is usually brownish, blue, green or black. This site has some pretty good information on goldstone;

If your specimen doesn't look like this you could take a clear picture, with something for scale in it, a coin works just fine, and resend the question.  With a picture I might be able to pin it down.  Another source would be your local university or college Geology Department.  They love to ID rocks for people.  Or a local rock club would be able to help.  This site lists the rock clubs in the U.S.;

Hope this helps.


All Answers

Answers by Expert:

Ask Experts


C. Robert Reszka, Jr.


I can answer any general geology question (rocks, minerals, stratigraphy, geomorphology etc.). My expertise is in the geology of the Michigan Basin, PreCambrian, Paleozoic and Recent. I can answer questions concerning mining and petroleum exploration and production and the laws concerning those activities. I can also answer questions concerning stratigraphy of the Michigan Basin. I will also answer questions about mineral and rock collecting in the Basin. I won`t be able to answer many specific questions on hydrology, geophysics or geochemistry. I may be able to answer very general questions in those venues.


I have been working for the State of Michigan for 36 years as a Geologist and a Resource Analyst. I have experience with Subsurface Geology and Petroleum Geology, mining in Michigan, and Sand Dune Mining and Protection issues.

Michigan Basin Geological Society

Decade of North American Geology.
Bedrock Geology of Michigan

BS Wayne State University

©2017 All rights reserved.

[an error occurred while processing this directive]