Thanks Jeff, I was thinking pyrite. I didn’t find this one. A mate of mine found it in Pine Creek, NT in a dry creek bed. He’s not a prospector and was just walking with his family and spotted it. I think it broke his heart when I told him i thought it was pyrite.Without the benefit of any standard mineral tests and just by the look, I’ll have a go with a sulphide mineral such as pyrite (iron);or chalcopyrite (copper iron). If under a high power hand lens the crystals are cubic then it would most likely be pyrite. A hot oxidizing flame test against it should show green if it was chalcopyrite.
These ores can also be auriferous.
If it is from an existing mine dump just look up mining records to see what was being mined.
If you have discovered an unknown seam of the material, it may be worth your while to take it to your states museum for identification. You don’t have to disclose the exact place you found it If you feel you may be onto something.
Just don't do this indoors, in case of Arsenopyrite.A little more on flame tests.
Copper is one of the easiest to identify in a flame test and in many cases is THE diagnostic test..
When doing a flame test ensure the sample is not placed in the blue part of the gas flame. The blue part of a gas flame is caused by oxidising methane and could confuse the colour signature. Where the blue finishes and the flame turns near or completely colourless is where the methane has completely burnt, is the hottest part of the flame and where the sample should be placed.
The thermal energy of the flame excites the copper ions and this energy is released as the copper ions cool down as they move to cooler parts of the flame. This energy is released in discreet packets as photons of different wavelengths representing different colours. Quantum mechanics in operation.
Unfortunately gold is not one of the elements that can be easily identified by this method as the energy levels required for ionising and exciting gold atoms would be far in excess of the hottest flame available to us. XRF type machines however can do this by using high energy X rays.
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