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Obsidian (volcanic glass)
Current inventory:  3 gems
 

Blue Obsidian

Chemistry:  70 - 75% SiO2 + MgO, Fe3O4

Prehistoric discovery;   IMA status: Not valid
The name Obsidian is supposedly from its discovery in Ethiopia by a man named Obsius.

 

Classification

   

   

Mineral Classification:

Amorphous (glass)

Strunz 8th Ed. ID:

n/a

 

 

Crystal Data

   

   

Crystallography:

Amorphous, no crystals

Crystal Habit:

n/a

Twinning:

n/a

 

 

Physical Properties

   

 

Cleavage:

Conchoidal

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.5 - 6.0

Density:

2.33 - 3.00 (g/cm3)

Luminescence:

None

Radioactivity:

Not Radioactive

 

 

Optical Properties

   

   

Color:

Black, Gray, Blue, Dark Green, Red

Transparency:

Transparent to Translucent

Luster:

Vitreous (glassy)

Refractive Index:

1.48 - 1.51  Isotropic

Birefringence:

0.000   (Isotropic)

Dispersion:

n/a

Pleochroism:

n/a

 

 

Occurances

   

   

Geological Setting:

Produced from volcanoes when certain types of lava cools rapidly by flowing into a body of water.

Type Locality:

n/a

Year Discovered:

Prehistoric

View mineral photos:

Obsidian Mineral Photos and Locations

 

 

More Information

   

   

 

Mindat.org

 

 


Obsidian, also known as volcanic glass, is a rock rather than a mineral that is a mixture of cryptocrystalline grains of silica minerals in a glass-like suspension. It is produced from volcanoes when certain types of lava cools rapidly by flowing into a body of water. Obsidian consists mainly of silicon dioxide. Obsidian is mineral-like, but not a true mineral because it has no crystal structure so it is amorphous. Otherwise, it is very similar in composition to granite and rhyolite. It is sometimes classified instead as a mineraloid. Obsidian is typically opaque black with occassional swirls of brown and not desirable for faceting. Rare occurances of transparent blue and green Obsidian have been found in various locations. These specimens make beautiful faceted gems with intense Sapphire blue and Tsavorite Garnet green colors. Obsidian is relatively soft (5.5 - 6.0) and brittle so usually not suitable for jewelry.

Green Obsidian:
This mysterious gem has been called many names including Green Obsidian, African Moldavite, Tanzanian
Tektite, Green Volcanic Glass and even just glass. One source says the Tanzanian natives call it Obsidianite. It is reported to be found in alluvial deposits and in a river bed at the base of Mt. Kilamanjaro. Some say it is a natural volcanic glass, some argue that it is man-made glass, others claim it is of meteoric origin similar to Moldavite. Calling it "African Moldvite" is incorrect however, since Moldavite only comes from the Moldau River reqion of the Czech Republic. Where ever this material comes from or however it was formed, it is a stunning gem of the finest Tsavorite green color.
 

  
Obsidian gems for sale:

Obsidian-001
please click on picture

Gem:

Obsidian

Stock #:

OBS-001

Weight:

21.0805 ct

Size:

17.60 x 17.60 x 12.50 mm

Shape:

Custom Octagon

Color:

Blue

Clarity:

Eye Clean

Origin:

Hunan Province, China

Treatment:

None (natural)

Price:

$338.00    [ Make an offer ]

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

Obsidian-001
please click on picture

Please click on the pictures for a larger view. This beautiful gem was precision hand-cut with the the highest meetpoint accuracy and best critical angles in Munich, Germany. It is a custom octagon design with 53 facets (45 facets plus 8 girdle facets totaling 53).


Obsidian-002
please click on picture

Gem:

Obsidian

Stock #:

OBS-002

Weight:

29.9490 ct

Size:

24.63 x 21.05 x 14.10 mm

Shape:

Custom Trillion

Color:

Tsavorite Green

Clarity:

VS (natural gas bubbles)

Origin:

Mt. Kilamanjaro, Tanzania

Treatment:

None (natural)

Price:

$308.00    [ Make an offer ]

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

Obsidian-002
please click on picture

This gem was precision hand-cut in the USA. It is a custom elongated trillion design with 97 facets (plus polished girdles). It is the top color for material from this location with very slight inclusions of natural gas bubbles (otherwise eye clean).


Obsidian-003
please click on picture

Gem:

Obsidian

Stock #:

OBS-003

Weight:

6.1135 ct

Size:

10.07 x 10.04 x 7.07 mm

Shape:

Square

Color:

Blue

Clarity:

Eye Clean

Origin:

Hunan Province, China

Treatment:

None (natural)

Price:

$61.00

Pictures are of the actual gem offered for sale.
Gem images are magnified to show detail.

Obsidian-003
please click on picture

A beautiful Chinese Obsidian with a very fine blue color.


 

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