FMF - Friends of Minerals Forum, discussion and message board

[Jim]

I was curious if anyone had photos of collector quality trapiche emerald crystals. I've seen some photos of crudely developed or non-gemmy trapiches, but I'm conducting research on natural, gemmy examples.

Aside from what's found on Mindat and in the Barlow book, can anyone share photos of great examples?

Thanks!

[Jason]

I have seen a couple photos here and there..don't recall any that were gemmy or really nice..will have to look around..is the research just on trap. emeralds or other traps. like sapphires

[Elise]

I would also love to see emerald trapiche crystals in their natural state. Firsthand, I've only seen trapiche emeralds cut as cabochons; I've never seen the original unharmed crystals. There is a Van Pelt picture in the extraLapis Emerald issue of a group of cabbed trapiche emeralds alongside a crystal, but it is hard to see if the crystal is altered or much else about it. There are beautiful pictures of different types of trapiches in John Koivula's PhotoAtlas Vol. 3, including one which has a double core resulting from interlocked columnar growth. There is also an interesting one pictured in which the "spokes" themselves are emerald (instead of the black mixture of minerals) and the surrounding material is white - in that case, I wonder would a mineral collector leave the matrix? It would be interesting either way.

An aside regarding another trapiche in the beryl family, John (K) showed me an aquamarine specimen which was a cluster of long, very slender crystals, each ending in a flat termination revealing a trapiche structure! There is a picture in the Gems & Gemology Fall 2008 issue, page 276 of the same or similar cluster, along with a photomicrograph of the termination which shows the structure. In that report he wrote that these originated from the Erongo Mountains of Namibia. Starting from the center, the included "spokes" seem to fan out to the prism faces and the gemmy areas span the junctions of the faces in between the spokes (a picture would tell a thousand words here...). In the Van Pelt picture of the emeralds, it seems like the crystal has been pre-formed for cutting as its cross-section looks round ( ? hard to tell from the picture), and so it is hard to know if it is formed in the same way as the aquamarine. In both of John Sinkankas' books on Beryl, there are good overviews of the formation, but without color images of a natural crystal.

There are also corundum trapiches which I have seen in Thailand cut into cabochons; I believe from Burma. I haven't seen any of these as spectacular as the emerald and aquamarine trapiches mentioned above.

Best wishes,
Elise

[Jim]

Amethystguy and Elise,

Thanks for the information. I find all trapiche effects fascinating but my research is focusing on trapiche emeralds in their natural state at this time.

Funny you mentioned the "double core" trapiche emerald. That cabochon -- which seems unique to this point -- used to be in my collection. That stone and a large trapiche emerald showing chatoyancy were two of my favorites. Those gems were sold to a major collector for his research collection, so they're in good hands.

I'll definitely check out the other photos you mentioned Elise -- some of these I may not have seen yet.

Gracias!

[Elise]

The only other picture I find of a crystal in its natural state is again another Van Pelt showing a crystal looking down the c axis (G&G W 87, 240). It makes one wish for the Google Maps toolbar button that lets you rotate to street-level to take a look at all sides!

I looked through every book on beryl/emeralds and mineral portraits I have, including Ron Ringsrud's latest and some I'd put on a shelf of "I don't read this language yet." I just don't find any pictures of the unaltered crystals - they must chop them up immediately.

I happened to have everything out on trapiches writing about the crystallography, but I didn't really think about the lack of portraits of crystals to refer to. The cross-section of the aquamarine trapiches is perfectly hexagonal. Both of the Van Pelt gemmy emerald crystals (maybe they are the same crystal) are nearly round - am I missing something or has it been rounded?

I look forward to any images which members post in answer to Jim's inquiry!

[Matt_Zukowski]

Although I don't have a picture, I was shown a large gemmy trapiche emerald at this year's Tucson. If memory serves, it was 5-7 cm long and 1-2 cm perpendicular to the c axis. The gemmy regions were really gemmy and saturated in color.

[Jim]

Hi Matt,

Was the specimen polished in any way to highlight the trapiche effect?

Thanks,

[simonoff]

Here is one from the Smithsonian.

[Jim]

[simonoff]

Very approximate maybe 2.5 inches (6.3 cm) across.

No problem

I am thinking of going back very soon - if you need something else in the picture, let me know.

[Matt_Zukowski]

No, it was not polished in any way. It was in pretty good shape as a mineral specimen.

[Fiebre Verde]

For those interested in trapiche emeralds, the lead article of the last issue of Gems & Gemology (Fall 2015, Vol. 51, No. 3) gives a full update on this fascinating crystal habit.
Gérard

[Roger Warin]

hi,
I see I'm not the only one to admire Trapiches emeralds.
I saw 4 beautiful Trapiches at the last Munich Show.
I photographed under cross-polarized light one of them. We discover the crystal growth lines. Crystallization is one of the simplest methods to purify a mineral. The impurities are rejected in front of the solid phase taking shape.
This emerald comes from Muzo, Colombia. While other Muzo trapiches have rejected feldspars, this one had ejected carbonaceous impurities, always abundant in this Muzo shale.
That's what I think, do you?
Roger.

[Elise]

[Val]

Unique and exquisite Emerald specimen. An Emerald crystal with a scepter of an actual trapiche Emerald crystal and all gem. What a wonderful thrill to be the current care taker of this natures creation.

I have seen Trapiche sharp emerald crystals. I have a fairly large (3-4 cm. in length) and dark colored one that I will have to find in the collection and photograph. Usually they are sliced up for gem cabochons and rarely get offered for collectors of the complete crystal. My son lives in Bogata, Colombia for 15 years, involved in specimen procurement.

[Fiebre Verde]

[marco campos-venuti]

What about this?

[Roger Warin]

It’s time to listen a master of crystallography.

[Roger Warin]

Thank you very much Elise, Gerard.

The word Trapiche has its origin in the name of ore grinding rolls in South America. It's a geological concept, perhaps earlier.
Isabella Pignatelli and all describe the phenomenon very well.

As the birefringence of emerald is very small, I used a trick to increase the retardation and thus accentuate colorations.
A gypsum plate is inserted between the trapiche and the polarizing filter. Its function is to add a known retardation. Gypsum produces a 550 nm red retardation.
This view is with the gypsum plate inserted most areas shift to first order yellow whereas a few shift to low second-order blue color.
Of course the sample is not a thin section. Its thickness is 4 mm.
Just for fun.
Roger.

[NellsRocks]

Forgive my newbie question, but these photos look a LOT like our local chiastolite. Can anyone explain in simple terms how these "patterns" are formed?