COPPER Minerals, Ore and Gemstones

Book on minerals & rocks in Wyoming

“Iron is taken from the dust,

And copper is smelted from rock.

“Man puts an end to darkness,

And to the farthest limit he searches out

The rock in gloom and deep shadow.

“He sinks a shaft far from habitation,

Forgotten by the foot;

They hang and swing to and fro far from men.

“The earth, from it comes food,

And underneath it is turned up as fire.

“Its rocks are the source of sapphires,

And its dust contains gold.

“The path no bird of prey knows,

Nor has the falcon’s eye caught sight of it.

“The proud beasts have not trodden it,

Nor has the fierce lion passed over it.

“He puts his hand on the flint;

He overturns the mountains at the base.

“He hews out channels through the rocks,

And his eye sees anything precious." 

- Job 28:2-10

Books on mineralogy, and copper deposits, itled me to the conclusion there are many copper deposits with dozens upon dozens of cupriferous minerals and cupriferous ores. The one thing about the many copper minerals found in the world is that many are brightly colored making identification a lot easier for the prospector and geologist. And, if you are looking for other types of ore - such as gold, silver, platinum group metals, lead, zinc, molybdenum and many others, copper is more abundant and usually mobilized with other important metals during pyrometamorphism and hydrothermal activity. This means when metals are put into motion by heat, pressure, and fluids, they seem to bunch together and become trapped near the earth's surface in structures, or by chemically favorable rocks. So, when you see copper, be sure you look for other nearby valuables.

In the West, copper is not unique: and you will find in all over the hills in old mining districts in Alaska, Arizona, California, Colorado, Idaho, Montana, Nevada, New Mexico, South Dakota, Oregon, Utah, Washington, Wyoming. You can spend a lifetime trying to collect all of the copper minerals, but when you get close, someone will identify a new one that was previously unknown.  But the West is not unique, as many copper deposits have been found across Canada, Mexico as well as throughout the United States. In some places, there is such much copper, one could decorate a house or even a town with all of the copper. And for a lot of people, its hard to imagine so much copper and other metals and gemstones can be sitting right on the surface and much of it untouched and overlooked by others. 

Massive chalcopyrite (copper sulfide) from the
Ferris-Haggarty mine, Wyoming

Some copper minerals are used as semi-precious gemstones, but many are soft and must be protected. Others produce spectacular collector specimens, decorative stones and lapidary. There are so many copper minerals that when I was in graduate school, one of my office mates built a reputation and PhD dissertation on identifying previously undocumented copper minerals. There are a few copper minerals that are more commonly used in gemstones and lapidary and these include turquoise, chrysocolla, malachite, azurite, native copper and cuprite. 

In many of the Western States, the more one searches the mountain sides, the more copper minerals they will find, but in the copper state of Arizona - copper is literally everywhere! You will find it in the hills, basins, people's back and front yards and even in parking lots. The photo in the upper left is a boulder of azurite (blue), tenorite (black), dark red (cuprite) and minor malachite (green) from the Morenci, Arizona district. Imagine wearing that boulder as a pendant around your neck.

Gossaniferous (limontite, goethite) matrix with vugs filled

with azurite (copper carbonate), Absaroka Mountains,

Wyoming.

Although azurite (H=3.5 to 4), malachite (H=3.5 to 4), chrysolla (H=2.5 to 3.5) and tenorite (H=3 to 4) can produce extraordinarily specimens due to vivid color combinations, having a soft hardness precludes much use of these as gems because they are so easily scratched. Thus these and other soft copper minerals must be protected. Others such as turquoise (H=5 to 7) are more favorable for wear. Then there are the extremely colorful minerals such as covellite (H=1.5 to 2) and bornite (H=3 to 3.25) (also known as Peacock copper) that are unmatched in nature.

10% dilute HCl is used
extensively by geologists
to (1) tell if a rock or
mineral has carbonate.
and (2) reduce metallic
sulfides, oxides, carbonates
etc. to naive copper on
weathered rock hammers

HOW TO IDENTIFY COPPER MINERALS

One distinct characteristic of copper minerals is a reaction to dilute (10%) hydrochloric acid. Copper carbonates such as azurite and malachite will fizz when they a few drops of hydrochloric (muriatic) acid are dropped on them; and most copper minerals will replace rusted iron with native copper when the copper is wetted with hydrochloric acid. Geologists pack around old beat up rock hammers and place a few drops of weak hydrochloric acid on a mineral suspected to contain copper. Next they rub their rock hammers in the wetted mineral. After it turns to mud on the rock hammer, they clean off the mud with their fingers, and if the mineral contains copper, rusty scratches in the rock hammer will be replaced by native copper.