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Geology/Metal crystal


QUESTION: I found a metal crystal that seems very heavy, it is about 2" by 1.5" and weights 11.21 oz. It is silver in color, has crystals, it will scratch lightly with a knife blade, it is non magnetic, and doesn't tarnish when in water, can you help identify it ?

ANSWER: I would really like to give you an answer to what this rock is; however, the picture has too much light which causes it to reflect off of some of the crystal faces.  I believe that I can tell you what it is but I need a better (more detailed) picture and could you tell me what the color of the dust that you scraped from the rock is and where you found it (specific location) which will give me a clue about rocks in the are; therefore type.

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QUESTION: I took more pictures and it is hard as the flat surfaces are so shiny they reflect a lot of light. You can't scrape dust off of it as it is very hard and you just get a very small scratch using all of the force you can with a knife blade. I found it in my Mom's house after she passed away so I can't tell you where it came from. It is a very silvery grey and has a lot of small shiny flat spots like crystals. It is almost as shiny silver as aluminum foil and feels like lead but very hard. I thought it might be osmium , doesn't have any smell to it. This thing is driving me crazy trying to figure out what it is. When I found it I put it in the fish aquarium and it was there for 5 years and it looks just like it did when I put it in there , non corroded. There might be a clue as some of the material is a dark green as there are some small holes in it and what looks like where some of it has been broken off. I can't seem to scrape off the green with a knife blade it just gets shiny green ? I will likely ever find out what this is.

I believe, as I did before you sent me the new pics, that the rock is Niccolite.  Niccolite is a nickel arsenide, NiAs, containing 43.9% nickel and 56.1% arsenic.  It is however, a solid solution mineral, meaning that the arsenic can be and probably is replaced by antimony.

It also can have small quantities of sulfur, iron and cobalt, and sometimes the arsenic is largely replaced by antimony. I believe that the rock is not osmium because it is not shinny enough to be osmium; however most of the other criteria are similar.

There are two kickers.  Nickle erodes, over long periods of time, to green, you mentioned green color oxidation.  But the most significant kicker will be when you heat the rock if it smell like garlic?  A garlic smell is the smell of arsenic. Back in the 1800's geologists used blowpipes, which can heat up to about 2,500 C degrees to recognize difficult minerals.  Temperature is the best indicator of a mineral.  Now there are propane touches although I still like blowpipes better (more control). Just heat the rock at one location for a couple of minutes and smell the rock, if it smells at all like garlic it is an arsenide.  It possibly could be Arsenopyrite or Skutterudite but because of the green edges I believe it is Niccolite.  Below are all of the general characteristics of Niccolite. Note that the fracture should be Conchoidal which means that it brakes concave, which can also be a good indicator.  The one thing that kinda surprises me is the hardness.  A knife blade has a hardness of 5.5 whereas the hardness of Niccolite is 5.0 to 5.5 which means that the knife blade should not really scratch the rock but leave a minor indention.  If you really want to know for sure what the rock is take it to a local college of geology who will probably do and AA (atomic absorption) test on the rock.

Color   Pale copper red with blackish tarnish. white with strong yellowish pink hue on polished section strongly anisotorpic

Crystal habit   Massive columnar to reniform, rarely as distorted, horizontally striated, {1011} terminated crystals

Crystal system   Hexagonal dihexagonal dipyramidal

Twinning   On {1011} producing fourlings

Cleavage   {1010} Imperfect, {0001} Imperfect

Fracture   Conchoidal

Tenacity   Brittle

Mohs scale hardness   5 - 5.5

Luster   metallic

Streak   brownish black

Specific gravity   7.8
Pleochroism   Strong (reflected light)

Fusibility   2

Other characteristics   garlic odor on heating


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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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