FMF - Friends of Minerals Forum, discussion and message board

[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?

[Vinoterapia]

Hi Roger.

I do not know the meaning of the word "Trapiche" in the whole of South America, but at least in Venezuela, trapiche is a place where the sugar cane is processed to produce a highly alcoholic spirit, something like what in the US is known as "moonshine".

The cogwheels used to crush the sugar cane have some resemblance to the so called "trapiche emerald", thus probably that is the origin of the name.

Regards.

José Luis.

[Elise]