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I am not sure if this is in your field, but I found a rock that appears rusty on the outside. I cracked it open, and it was this glittery, silver color. Some of the inside is slightly yellow tinted, like a dull, ugly yellow. Neither me nor my parents can tell, nor identify it. My dad thinks it might be some kind of crystal. It is not magnetic.

Yes it is in my field and it sounds like pyrite. The mineral pyrite, or iron pyrite, also known as fool's gold, is an iron sulfide with the formula FeS2. This mineral's metallic luster and pale brass-yellow hue give it a superficial resemblance to gold, hence the well-known nickname of fool's gold.

Being partially composed of iron (Fe) when oxidized will turn into rust (rusty on the outside) and (slightly yellow tint) partial oxidation of Fe. If it is pyrite it should be magnetic after heating to about 1,500 degrees F.  

Pyrite is the most common of the sulfide minerals. The name pyrite is derived from the Greek πυρίτης (pyritēs), "of fire" or "in fire",in turn from πύρ (pyr), "fire". In ancient Roman times, this name was applied to several types of stone that would create sparks when struck against steel; Pliny the Elder described one of them as being brassy, almost certainly a reference to what we now call pyrite. By Georgius Agricola's time, the term had become a generic term for all of the sulfide minerals.

Pyrite is usually found associated with other sulfides or oxides in quartz veins, sedimentary rock, and metamorphic rock, as well as in coal beds and as a replacement mineral in fossils. Despite being nicknamed fool's gold, pyrite is sometimes found in association with small quantities of gold. Gold and arsenic occur as a coupled substitution in the pyrite structure. In the Carlin–type gold deposits, arsenian pyrite contains up to 0.37 wt% gold.

If you can send me a couple of pictures I can confirm my thinking that this is pyrite.


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Joe Norris


I am an economic geologist. An economic geologist does mineral evaluations and appraisals of mineral or mining properties. I can tell you if your deposit has value - remember that a mineral deposit, no matter how good, only has value when mined. Any value assigned to a mineral deposit, in the ground, is only the speculative value that deposit.


I have been a economic geologist for most of my 35 year career. Although I have done work in perhaps 45 states and numerious countries much of my work has been in Appalachian coal, intermountain west gold and silver, and Arizona uranium.

Past President of the Virginia Section of the American Institute of Professional Geologists and a certified geologist in twelve states.

BS Degree from Eastern Kentucky University. Work on MS Degree @ Eastern Kentucky University, Colorad School of Mines & Marshall University Numerious short courses on the value of mineral deposits and how to value same. Also several short courses dealing with the different types of geologic processes; sedimentary, igneous, metamorphic along with the mineral associated with each.

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