HISTORICAL PAPER ON - GRAY COPPER
GRAY COPPER
Was just rerading up on the " gray copper " and i shudder the thought of how many juniors out in field would never even think to look for the " gray copper " rather, focusing on the typical, yellow chalcopyrite, azurite blue, or malachite green.
The more i read up on copper, it appears to be a - tricky mineral.
Seems it can hide amongst other minerals - paired or in transition, with compatible bond. Yes, copper can be - quite elusive.
Question is put forth,
Most al lminerals have a measure of impurities,
Copper, specifically sulphides, are not with 100 % - they usually are in a bond of other minerals such as - iron, bismuth, salts, silver, etc...
Let's suppose a mineral specimen was with several other impurities -
silver - 50%
copper - 40%
antimony - 3%
Magnesium-3%
Calcium - 2%
iron - 1%
silica - 1%
NOW - would a spectometry test prefer detect only the dominant silver ?
would it be able to pickup the -copper ?
Perhaps it all depends upon how the spectrometry machine was - calibrated.
something to ponder.
GRAY COPPER - HISTORICAL
https://www.google.ca/books/edition/The_U_S_Naval_Astronomical_Expedition_to/nh1LAAAAYAAJ?hl=en&gbpv=1&dq=gray+copper&pg=PA90&printsec=frontcover
My second thought was....
if most juniors only seek the typical copper then..,
how many copper depoists have been overlooked if copper can hide itself
as a - gray mineral ?
Here's a quick review on different kinds of assaying -
I chose this liberation analysis out of several other assaying methods in the link below.
Liberation Analysis: Liberation analysis is dedicated to analysis of particles and grains in the sample and provides information about their size, density, texture, as well as mineral and elemental composition. Grain-by-grain processing of all particles in assayed samples allows detection and evaluation of various types of ore particles and offers data essential for i.e., ore processing control or heavy mineral studies.
COLORADO SCHOOL OF MINES
https://geology.mines.edu/laboratories/automated-mineralogy-laboratory/
MINDAT - COSELITE
Another mineral called - Coselite - has impurities of copper.
Color of minerals - you guessed it - Gray.
Though the formula for coselite is - Pb2Bi2S5 ( lead, bismuth, sulphur )
Others who've detected copper in Coselite rewrote the formula as -
EXCERT -
Appears to contain Cu and Ag as apparently essential constituents, according to Clark (1993) ("Hey's Mineral Index") and Zak et al. (1992) and the detailed study of Topa & Makovicky (2010). The latter propose the general formula CuxAgi+sPb8-2s-0.5(x+i)Bi8+sS20; they state: cosalite is "a unique case of solid-solution based on a combined omission-interstitial insertion substitution".
If one scrolls down page in link below - there's another coselite formula containing
copper - proving that copper can be quite elusive hiding amongst other gray colored minerals - even covellite is yet another form of - gray copper.
https://www.mindat.org/min-1139.html
Anyways,
I'll shut up about the copper.
It's just after seeign Copper Mountains ores beign of grey color and they mine copper, and seeing Darmara having sililar colored ores in hte trenches or on Placer mountain - i said,
i better mention grey copper... lol