FMF - Friends of Minerals Forum, discussion and message board

[Howard Heitner]

This specimen was only labeled dioptase from Tsumeb, There is obviously something else on the matrix. I was told that it might be dolomite or minrecordite, Are there any other possibilities? Can it be identified without sending a small piece to a lab? No specific mine or level is known.

[Matt_Zukowski]

It certainly could be minrecordite - see:
https://www.mindat.org/photo-1284257.html

[Howard Heitner]

I am very surprised that such a rare mineral or any other mineral was not on the label. The picture does not show the side where most of the dioptase crystals are, Looking closely at that side, it looks like the second mineral formed on top to the matrix and the dioptase formed on top of that layer. Does that have any significance?

[Jordi Fabre]

Sorry if I sound like a party pooper, but I’ve had several 'Minrecordite' before, and so far, after being analyzed, they have always turned out to be Dolomite.

I suggest analyzing the sample.

[Howard Heitner]

That has been suggested to me. Would an elemental analysis by EDX be enough.?

[alfredo]

"Would an elemental analysis by EDX be enough.?"

In my experience, EDX does a poor job with light elements like Mg and C. So unless you are performing the analysis on a flat polished surface, by an experienced operator, and you get a result far away from any series midpoints, you can't be certain.

[Howard Heitner]

Would not the presence or absence of zinc be sufficient to tell the difference? It is not a totally unknown mineral. It either has zinc (minrecordite) or not (dolomite)

[Marvin Hanner]

Howard, The photo, while nice, does not show sufficient clarity to tell if the unknown is minrecordite or not. Minrecordite crystals are ALWAYS twisted, saddle shaped like a lot of the pink dolomite from our midwest. Even it they did contain zinc it would not prove they are minrecordite, only that they were zinc containing dolomite. The crystals could be tiny calcite crystals; again the photo does not show sufficient detail to show if they are tiny rhombohedrons. Marv

[Roger Warin]

About Minrecordite and about light
Hello
I bought this beautiful Minrecordite sample in 1984.
It is type A. I don't know what that means.
The tiny rhombohedrons of minrecordite surround splendid dioptase crystals. Jewels!
But modern photons aren't the same as in my day! Dioptase looks like tanzanite.
Impossible to correct the hue. However, the greenish shadow is cast on the nearby minrecordite crystals.
I ask for advice.
In the sun, with a Nikon D800E + Mikronikkor, I find the dioptase (badly).

[Herwig]

Bonjour mon cher Roger!
I don't understand where the "type A" comes from. Maybe it is on the label? Can you please show us the label of this specimen?

minrecordite is a member of the dolomite group, and the group members that have Ca (=calcium), are:
minrecordite : CaZn(CO3)2
dolomite : CaMg(CO3)2
kutnohorite : CaMn2+(CO3)2
ankerite : Ca(Fe2+,Mg)(CO3)2

In order to have minrecordite, there needs to be enough zinc (=Zn) present.
An EDX that has been calibrated correctly, should be able to tell you the amounts of Zn, Mg, Mn and Fe that is in the material, and that will tell you if it is minrecordite or not.
HTH - Cheers, Herwig

[Howard Heitner]

This is a closeup of the unknown mineral taken with my macro lens. I am not set up for microphotography. Does it help with identification in any way?

[Matt_Zukowski]

A better picture won't help. You'll need to have it analyzed as discussed above.