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stone from the outside
stone from the outside  
stone from the inside
stone from the inside  
QUESTION: i found these stones inside a rock, will you please help me knowing about it? the stone is black and grey from the outside and silver from the inside, it is heavy and sorry i have no clearer photos.. plz if you have any idea contact me asap..thank you

ANSWER: Hi Sirine,
You have a couple of very nice pyrite nodules.  Pyrite is a mineral made up of Iron and sulfides.  

It is often called "Fool's Gold" because of it's close appearance to gold.  It generally is brassy yellow and forms very good cubes; here's a couple pretty good pictures of a type of

The above images are of very good quality pyrite crystals but you have a nodule which is a cluster of crystals that grew all together.  The surface of pyrite can weather to a rusty brown and look much like yours.  Here's an example that resembles your specimen:

Your picture is pretty fuzzy but all the little points and edges are parts of the pyrite crystals that a poking out of the nodule.

Sometimes the nodule can be cleaned up (brushed with soap and water or an iron solvent) and it can look like this:  

There is another mineral called Marcasite that resembles pyrite but the color is more silvery on a fresh surface.  The broken pieces you show look more yellowey.  A good way to tell the difference between the two minerals is to check out their streak.  A "streak" is the color of the powdered mineral.  All you need to do is scratch the mineral on unglazed porcelain.  The color of the pyrite powder will be a greenish-black to brownish-black while the marcasite will be just black.

Hope this helps.

---------- FOLLOW-UP ----------

QUESTION: Thank you for the answer Mr.Bob. here are clearer picture of the stones i have just to make sure.
I would like to ask you if they are an important stones and if they can be sold?

Hi again Sirine,
Thanks for the pic.  They do look like pyrite nodules.  Pyrite does have modern uses; the paper industry uses the sulfur dioxide that's made from it, sulfuric acid is made from it, and it's used in lithium batteries.  But those uses are only in large quantities.

What you have might be interesting to collectors but I don't know how you can notify them in your area.  Also, they look like specimens good for entry level collection, which means they aren't very exceptional.  They are nice but not worth very much.

Hope this helps.


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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

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