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[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.

[Michael Shaw]

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 ( https://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.