How to Identify Copper Ore

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How do you identify copper ore in the field?

This is not meant to be a fully comprehensive guide just some quick simple tips when in the field. 

 Typically copper ores form in hydrothermal systems where hot water is circulated through fractures in rock depositing valuable minerals. A prime place to hunt is fractures in specific rocks to spot minerals and the larger fracture and fault zones that form in rock units as a general area. If you are lucky you may come upon a massive volcanogenic deposit but those are typically located inside mining jurisdictions. 

Minerals commonly associated with copper include pyrite, Galena, sphalerite, Hematite, and magnetite. The list provided is just the most common and easily identified to point you in the right direction. 

Start with the mineral type present. Are you dealing with silicate and carbonate rocks, granite or limestone usually, or sulfides that have pyrite for example? If you're not sure, are you seeing metallic minerals or green and blue? Sulfides appear metallic and the silicate and carbonate copper minerals appear green and blue. Note the green in the photo above in the center area. These mineral types can occur together but are chemically quite different. They represent much different grades of copper and would be processed differently. 


Note in the photo above the green silicate copper minerals and the darker sulfide minerals just below the green. The photo below shows Malachite in green and azurite in blue. That sample is from Jerome Arizona. 

There are two greens to look for with copper minerals. A light pale green, almost pale Turquoise, is characteristic of the copper silicate chrysocolla. A darker rich deep green is typical of Malachite, a copper carbonate. Malachite is higher grade than chrysocolla. The two different greens are visible in the image below near and below the center of the image. 


Copper sulfides tend to be much higher grade than carbonate and silicate by weight percent copper. Look for iridescent metallic minerals, typically those will be chalcopyrite and bornite. Chalcopyrite is more golden colored and bornite is very heavily iridescent throughout. Some veins of copper sulfides are shown below. Dominantly chalcopyrite. Some darker bornite is visible in the lower right of the sample.


There are rare occurrences of native copper that appear exactly as pure copper does. They also commonly tarnish to black. More exotic copper minerals than described above exist but are uncommon outside mining jurisdictions and are unlikely to be found by us regular folks. 

The photo below shows chrysocolla with accessory Malachite on calcite.

Some handling tips: scrub your samples with a dry brush first, then use a wet one. Do not use acids on copper minerals as most are soluble or will get heavily oxidized. Be gentle with Malachite as it's not very hard, and with sulfides as they tend to be friable or brittle. Chrysocolla is a harder silicate and can typically be scrubbed fairly aggressively. 

Copper ore is typically for sale at the BJ Spud Ranch shop linked below:

https://bjsspudranch.etsy.com

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