Does iron make turquoise more green and copper make it more blue…..or Vice Versa???

Hi Paula,

I hope you can settle a bet I am in with my boss and co worker. We all work at a store that has the biggest collection of dead pawn jewelry here in xyz. Great museum worthy collection. Both my boss (owner of the shop) and co worker tell our customers that the color of turquoise is dependent on blue being more iron and green being due to more copper present. That is the exact opposite of what I learned as a life long rock hound and native jewelry collector / enthusiast. Their argument is that Bisbee has iron matrix (hematite mostly) and it is the famous Bisbee blue, and not so much green. There is also Morenci, which is noted for the iron pyrite, and is typically blue. Although I have seen some pretty green Morenci as well. They claim that since pyrite and hematite are both iron and appear in these noted “blue” turquoises, then it is iron that gives the blueness. My boss also tells people that the matrix in Royston is copper. Which sometimes the copper does actually appear in the matrix, but mostly I thought it was limonite or rhyolite. The copper usually seems deeper and will darken with age, like a penny does. But the limonite or rhyolite remain the same.

Morenci Turquoise

Royston Turquoise

I showed them I could not force google to say blue is due to iron and green is due to copper. Is always says the opposite, or “did you mean green is due to iron presence?” or “did you mean blue is due to copper presence?” But they still won’t believe me, or google. Do you have any resources that I could use to show them? I’m not trying to be a know it all, I just don’t want them perpetuating bad info. Please help!

Thanks!

Hello,

We are NOT rock “experts” but we do have a fair bit of knowledge and
experience among us.

All of us here agree with you, as evidenced by the content of some articles from our website and this blog.

“The more blue, the higher the copper content. The more green, the higher the iron content.”  Turquoise and Mines  and Green Turquoise

As you will read in various articles on our website, some turquoise will turn green as it ages due to effects of oxidation, dehydration and exposure to the elements and products (lotions etc.). So turquoise once blue will sometimes end up green – that’s why you see more green turquoise in vintage pieces.

Here are some other internet sources – there are many.

“Also, within the same mining operation, sometimes within the same vein, both greens and blues will be found. The blue is the copper, and greens are molecules of zinc or iron. So value is not necessarily based on color even though blue does often sell for more because more people prefer it.” Learn about Turquoise

“Colour is as variable as the mineral’s other properties, ranging from white to a powder blue to a sky blue, and from a blue-green to a yellowish green. The blue is attributed to idiochromatic copper while the green may be the result of either iron impurities (replacing aluminium) or dehydration.” Wikipedia

The Wikipedia article has references that might lead you to more technical information should you desire it.

Like you, I could not find any reference to copper being associated with green turquoise and iron being associated with blue. It was always the other way around.

A fun thing to google is copper sulfate – hit images and wow, is that blue or what ??!! I don’t know if this has any relevance, but here copper definitely = blue.

Copper sulfate

I hope others might weigh in on this topic because I am not a geologist by any stretch of the imagination !

I wonder if some people associate green with copper because copper pennies can turn the inside of your wallet green. And copper roofs turn green over time depending on the climate and location. And copper bracelets can turn the skin of some people green. But that is a whole other topic related to oxidation and acidity.  Maybe that is where the confusion lies?

Green Patina on Copper Roof

Paula