Obsidian | Gemopedia

Obsidian is formed by the rapid cooling of viscous lava due to volcanic explosions. It consists of the same minerals as granite, but cools so quickly that they do not have time to crystallize. Obsidian has a glassy luster and is usually black or a very dark green, but it can also be found in an almost colorless form.
Alternate
Names
Banded Obsidian, Onyx Obsidian, Sheen Obsidian, Snowflake Obsidian, Rainbow Obsidian, Apache Tears
Colors
Gray To Black, Brown To Brownish Yellow, Orange, Red. Rarely Blue, Green, Purple.

Obsidian Classification

Common Name

Obsidian

Species

NA

Variety

Colors

Gray To Black, Brown To Brownish Yellow, Orange, Red. Rarely Blue, Green, Purple.

Alternate Names

Banded Obsidian, Onyx Obsidian, Sheen Obsidian, Snowflake Obsidian, Rainbow Obsidian, Apache Tears

Gemstone Groups

Key Separations

RI, SG magnification and appearence

Comments

Natural glass; Misnomers: fire pearl, agni mani, glass agate, Montana jet, mountain jet, mountain mahogany, Nevada diamond, Nevada topaz, tokaylux sapphire, Iceland agate

Obsidian Optical Properties

Transparency

Transparent - Opaque

Refractive Index

1.49
Tolerance:(+0.020/-0.010)

Birefringence

Optic Character

NA

Optic Sign

NA

Polariscope Reaction

Singly Refractive (SR) With ADR

Fluorescence

SWUV: Inert
LWUV: Inert

CCF Reaction

Pleochroism

None

Dispersion

Strength: weak fire Value: 0.01

Comments

Obsidian Chemistry & Crystallography

Chemical Name

silica

Chemical Formula

SiO2(MgO,Fe3O4)

Synthesis

Crystal System

NA

Classification

Nature

Natural

Crystallinity

Amorphous

Comments

Obsidian Characteristic Physical Properties

Hardness

5-5.5

Streak

White

Specific Gravity

2.33-2.6 Typical:2.4

Toughness

Varies

Inclusions

Obsidian often has gas bubbles, cristobalite inclusions and stubby needle like inclusions. Banded obsidian: curved or sinuous bandsMacusanite: pale yellow to greenish obsidian from Peru. Mahogany obsidian: red and black banded material. Onyx obsidian: straight, parallel bandsSheen obsidian: silvery or golden looking sheen caused by gas bubbles Snowflake or flowering obsidian: white patches of cristobalite inclusions on a black backgroundRainbow obsidian: rainbow iridescent colors caused by numerous tiny bubblesApache tears: small, rounded irregularly shaped black nodules found in the American Southwest.

Luster

Vitreous

Stability

Fracture

Conchoidal

Cleavage

None

Comments

JTV on Google+
0 Items
My Wish List
Close
Item
Description
Qty.
Price


Estimated Order Total:
0
Total Due Today:
0
Close
Item
Description
Qty.
Price


Page of 1