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[Fiebre Verde]

[Fiebre Verde]

2 intergrown beryl crystals with a pronounced grayish tone partly caused by black carbonaceous impurities.
Note the cloudy aspect of the inclusions at the very base of the main crystal.
The French call the emerald's inclusions its 'jardin' (garden).

[Fiebre Verde]

A common Peñas Blancas association of white and iron-stained calcite.
Only quartz is missing!

[Fiebre Verde]

Iridescent dolomite is relatively common in the Colombian emerald districts.
What is less common is to see this feature on emeralds.
The flat basal termination of this crystal is actually not completely flat and iridescence occurs on 2 patches which are slightly tilted with regard to the c-axis termination.
Matrix is white calcite.

[Fiebre Verde]

2 beryl crystals in a coal-black matrix.

[Fiebre Verde]

The large contact area does not seem to affect much the glowing effect of this crystal.
Host rock is black shale.

[Fiebre Verde]

The La Pita district was named after the original La Pita mine which opened in 1997.
The Polveros mine opened shortly after and has produced fine specimens ever since.
The other mines, Cunas, Totumos, and Consorcio which are all separately owned make up a vast complex of interconnected shafts and galleries which has lead to endless disputes and conflicts.

[Fiebre Verde]

Yet another oddity from Chivor.
Apart from its clarity, the interesting feature of this aggregate is the large notch in the upper part.
It does not show very clearly in the images but the internal faces of the notch are as glassy and smooth as the faces of the aggregate.
So could that be a weird growth feature or just a contact deformity that has recrystallized?

Host rock is black shale.

[Fiebre Verde]

From Polveros to Cunas.
Host rock is black shale.

[Pierre Joubert]

Just so Beautiful!!! We love the rainbows too.

[Fiebre Verde]

[Fiebre Verde]

Another spectacular "rainbow" effect from Polveros.
As I mentioned in a previous post, iridescent dolomite is quite common in both emerald belts. But some, like this one, are quite spectacular.
I was confused with the stepped cube crystal featured in IMG_9512nb and thought at first it was colorless fluorite but after close examination I am pretty convinced it is a dolomite rhomb.
Host rock is black shale.

[Fiebre Verde]

Another specimen from La Pita.
Iridescent calcite this time (last image).
Host rock is black shale.

[Fiebre Verde]

Let's have a small break from Colombia.
Well... not quite :-)
This Panjshir beryl has a tone that reminds of the famous Muzo deep green.
Matrix is a siliceous metasedimentary rock scattered with tiny pyrite nodules.

Emerald production in Afghanistan is erratic and never high. As a result it is difficult to get hold of any specimen from that country these days.

[Fiebre Verde]

Aggregate from Chivor on a snowy white albite matrix.

[Fiebre Verde]

Calcite is unusually transparent and has a remarkable luster in this La Pita specimen. Some of these crystals are striated.
Host rock is black shale.

[Fiebre Verde]

This Coscuez specimen puzzles me.

If we assume these 2 half crystals were originally part of one single complete beryl crystal, I don't understand the mechanism which made them crack apart along the c-axis.
Cleavage in Beryl is poor and parallel to the base.
I am not sure either on the filling mineral id which has a strong pink cast.

And, oh yes, I don't think it's glued.

[Fiebre Verde]

Chivor, what else?

There are 2 generations of dolomite: aggregate of small (millimetric size) pale brownish rhombs covering a bed of white albite and isolated lustrous colorless crystals.
Can't figure out what's the light-brown aggregate formation also featured in this specimen. Possibly halloysite balls? (can be seen in all images).

Host rock is a grey limestone shale.

[Jamison Brizendine]

Gérard,

I love your unusual Coscuez emerald (IMG_9915nb.JPG)!

I have a PDF copy of Ron Ringsrud’s article on the Coscuez Mine, from Gems and Gemology. I took a quick glance, but he mentions that the Conscuez emeralds are often found in faults along the Lower Cretaceous Villeta Formation (120 - 130 ma). He mentions that the area has undergone both ductile and brittle deformation.

To me your poor emerald was tectonically fractured by extension, and then filled in with some calcite. I have seen many examples of photographs of “normal faults”, but this is the first example I’ve seen of a “normal fault” which shows a gem mineral as what is being offset. What a cool oddity!

References Cited:

Ringsrud, R., 1986, The Coscuez Mine: A major source of Colombian emeralds: Gems and Gemology, 22, p. 67-79.

[Fiebre Verde]