FMF - Friends of Minerals Forum, discussion and message board

[Fiebre Verde]

Another glowing crystal, just for Tobi :-)
Host rock is black shale.

[Fiebre Verde]

This specimen is from a relatively recent find (2010/11) from the El Acuario mine, in the Eastern Belt.
The gray shale host rock is coated by a layer of pyrite nodules.
Another characteristic of this pocket is the pencil-shaped emerald crystals.
They are usually short (less than a centimeter) and contain very few inclusions.

[crosstimber]

I love the complex terminations on this last specimen. Wonderful.

Michael

[Fiebre Verde]

[Fiebre Verde]

Back to the Western belt with a Polveros specimen.
Polveros is the southernmost locality of the La Pita mining district.
Emeralds from this locality tend to be less saturated than in Cunas or La Pita (La Pita name refers to a locality and a district - a bit confusing!).
White and semi-transparent striated calcite on black shale.

[Tobi]

That clear crystal on IMG_0985nb.JPG ( http://www.mineral-forum.com/message-board/download.php?id=63661 ) with its great terminations, so beautiful!

[Fiebre Verde]

[Fiebre Verde]

When it comes to minerals, Colombia is mostly known for Beryl, Euclase and, to a lesser extent, Parisite.
But this does not do justice to the Colombian quartz.
Peñas Blancas is known for producing emeralds but also for its beautiful clear colorless quartz.

This specimen features a quartz cluster with some very clear crystals.
The emerald is nested right in the center of the cluster and has the typical Peñas Blancas velvety appearance.
Color is very slightly bluish green.

[Fiebre Verde]

Although less spectacular than in Peñas Blancas, water clear quartz can be also found in Muzo.
The tip of the (only) quartz crystal of this specimen is party visible at the bottom-center of #1643.
Host rock is black shale.

[Fiebre Verde]

Too good to be true, highly suspicious position of the beryl crystal with respect to the matrix, and so on....
Of course, this came immediately to my mind when I first saw this specimen.
At that time (2009) a new pocket had just been found in Polveros.
Unfortunately the emeralds were far from being clean and were lacking color.
But the quality of the calcite crystals was good enough to justify some "art work" by the local craftsmen.
The way the beryl prism is contacted in several points at its base rules out any fakery.

Host rock is black shale.

[Fiebre Verde]

Emerald aggregate from Muzo.
Host rock is black shale.

[Fiebre Verde]

From the La Pita district.
Host rock is black shale.

[Fiebre Verde]

This Muzo specimen baffles me.
Can't figure out what's the anthracite/graphite-like material coating the shale matrix (see last image for close-up).
I have never seen this crystal habit in Muzo or any nearby locality.
Could that simply be... black calcite?
In some areas, some white calcite is squeezed between the shale host rock and that mysterious black material.

The beryl crystal was broken into two parts and the fracture was filled with that material.
Although not equally developed, first and second order prisms are clearly visible.

Very interested to hear your suggestions and ideas!

Gérard

[Jordi Fabre]

[Fiebre Verde]

Thanks Jordi.
Could also be the result of a graphitization process of carbonaceous material?
It does leave black marks on paper but so does carbonaceous black shale.
Not a big deal - will tag this as consolidated carbonaceous debris.

[Fiebre Verde]

Dolomite crystal and emerald cluster over a white calcite rhomb.

[Fiebre Verde]

Main crystal is double terminated.
Host rock is black shale.

[Fiebre Verde]

In September 2015, the UK-based mining company Gemfields has entered into binding agreements to acquire controlling interests in two emerald projects in Colombia, one of them being Coscuez. At completion, Gemfields will acquire an indirect 70% interest in a Colombian company which will hold the mining contract for the Coscuez mine.
It's still too early to measure the impact of this major takeover on the specimen production from this historical mine.

[Fiebre Verde]

Not the most aesthetic specimen of my collection but probably the most exotic one.
I found this specimen in a European show, 7 years ago. The label mentions Peñas Blancas for the locality name but nothing is less sure.

Assuming it's not a fake (which is a reasonable assumption considering the poor quality of the apatite crystals and the way they are contacted by the emeralds from almost every side), here is the dilemma:
1) The only Colombian locality producing/having produced pink tabular apatite is La Marina mine which is located right in the heart of the Western Emerald Belt.
2) The Mindat mineral list for La Marina is limited to albite, euclase and apatite. Never heard of any emerald occurrence in La Marina, even from the most enthusiastic dealers in Bogota (I like to challenge them but that's another story...)

Of course, the other option is that it's not Colombian.
It is reported that pink apatite, beryl (variety emerald) and albite (variety cleavelandite) can be found in the Laghman pegmatite province in Afghanistan. But Laghman province is vast and these minerals do not necessarily coexist in the same locality. Not even mentioning that Laghman emeralds are known to be embedded in schist matrix.
So Laghman is a very remote possibility...

In the absence of further evidence, I will label this specimen as Colombian.

Matrix is highly oxidized albite.

[Josele]

Really an interesting piece!

A quick search in mindat gives more examples of Colombian emerald-apatite combinations:
http://www.mindat.org/photo-66089.html
http://www.mindat.org/photo-66130.html

If it is not Colombian, could be also from Pakistan.

Did you check the fluorescence?