FMF - Friends of Minerals Forum, discussion and message board

[Roger Warin]

Tsumeb - Deposit of dioptase on calcite.
Otjikoto Region, Namibia.

A colorful specimen with deep green Dioptase crystals twinkling on Calcite rhombohedra.

This subject has already been presented on FMF but I have not found it.
Here is a specimen from the Willy Israel collection.

Even in 1986 in Tsumeb, these calcite dioptase specimens were rare.
A 1st generation of calcite rhombohedra received a deposit of small crystals of dioptase (~ 1 mm), usually on only one face of the rhombohedron (partial perimorphosis?).
Further, the size and orientation of the crystals are arbitrary.
Then, the calcite resumed its growth in parallel axes, the source of dioptase then being exhausted. This 2nd calcite growth thus forms a nice frame around the slightly bluish green dioptase crystals.

[SteveB]

A rather attractive specimen. The contrast of the “framing” really makes you think about how it could be natural. It's just too perfect and far from the norm - I have to stop and marvel at the natural world. Similarly I’m drawn to the Pike’s Peak clear Fluorites with purple corners. Just something I find so beautiful in the ordered patterns of both. Unlike regular crystals or twinned of other minerals where perfect examples are uncommon and wonderful, these and the fluorites are just another level of “wow” beyond. Thanks for sharing.

Steve

[Roger Warin]

Thank you for your comment.
Nature is beautiful because it often shows a state of balance.
I did not understand why the dioptase was deposited on a face of the rhombohedron, but this is not due to chance.
If any of the forum members could come up with their idea, it would be nice to discuss it.
Taking macrophotos causes the discovery of strange things.

[SteveB]

Sorry I misread the first post, I thought you understood the formation and didnt get the single side part either.

I‘ll spitball my ignorance.
First is this a specimen you own snd can examine?

Are the dioptase faces all facing the same way?
Are the clean calcite frames a little higher than the dioptase?

I imagine the calcite cubes formed to the size of the current dioptase areas wherupon the dioptase was introduced into the environment and then ceased/depleted while the calcite solution allowed the cubes to continue growth, giving the result.

Just a thought.