Gemstones and Glass

[morecarats]

Here''s a gemstone riddle for you ---

My friend bought some some gemstones at a gem show, but two of the gems, each a different variety, tested as glass.

I commisserate with my friend, and advise him to be careful who he buys from. But to my surprise, he replies that he got exactly what he expected with those 2 gems.

Question: what kinds of gems did he buy?

 

[davi_el_mejor]

Date: 6/24/2010 4:50:43 AM
Author:morecarats
Here''s a gemstone riddle for you ---

My friend bought some some gemstones at a gem show, but two of the gems, each a different variety, tested as glass.

I commisserate with my friend, and advise him to be careful who he buys from. But to my surprise, he replies that he got exactly what he expected with those 2 gems.

Question: what kinds of gems did he buy?

It''s very late (for me at least) and all I can think of is obsidian (I''ll try again after not working 5pm to 5am)

 

[iLander]

Here''s my guess: tecktite?

That is the full extent of my knowledge on the subject.

I would like to know more about this type of glass, so please tell us about it.

If that is the answer . . .

 

[chrono]

Obsidian and Impactite (Libyan glass)?

 

[morecarats]

Well done all! The correct answers (so far as I know) are obsidian (volcanic glass) and moldavite (tekite), also know sometimes as impactite since this rare natural glass is formed from condensed rock vapors after a meteorite impact.

Just a reminder that sometimes (not often), when you buy glass, you''re getting a real gemstone.

 

[chrono]

This is fun! I hope we''ll have more of these quizes.

 

[iLander]

Is this what prompted the thread, morecarats? Barry''s latest update? I think this is really an unusual stone so I grabbed it for a tie tac for my DH.

Here''s the description from the site:

MD-6118 Moldavite(J/D) 3.58 cts., 11mm trilliant[Gec]. Found in the Czech Republic, this gem is a form of tecktite, possibly resulting from a large meteorite strike 14M years ago that formed the Riess Crater near Stuttgart, Germany. It is a fascinating gem material and a piece of cosmic history.

As far as I can tell, most tektites are black and opaque and only the ones from this particular area are green.

I''m interested to read more info, so please expand on it, Morecarats.

 

[morecarats]

I started thinking about natural glass when I was researching the different kinds of non-crystalline gems. Most non-crystalline gems -- such as pearl, amber, coral, jet and ivory -- have an organic origin. But moldavite and obsidian were formed by cataclysmic events -- volcanic eruptions in the case of obsidian, and meteorite impacts in the case of moldavite. The material cooled rapidly without crystal growth. Like other forms of glass, they are singly refractive.

Moldavite is found in only in the southern Czech Republic, where there are 4 mines currently operating. It is estimated that the supply of gem quality material will be gone in about 10 years.

Moldavite is one of those gems which are often accompanied by outrageous claims. Because it is thought that modavite is formed as a result of a meteorite impact, you''ll hear it referred to as "the gemstone from the stars," implying that the material is of extraterrestrial origin. However, analysis has apparently shown that moldavite is simply silicon dioxide and aluminum oxide from right here on planet Earth.