Structure

Obsidian is a naturally occurring volcanic glass formed as an extrusive igneous rock. Obsidian is produced when felsic lava extruded from a volcano cools rapidly with minimal crystal growth. It is commonly found within the margins of rhyolitic lava flows known as obsidian flows, where the chemical composition (high silica content) causes a high viscosity, which, upon rapid cooling, results in a natural glass forming from the lava. The inhibition of atomic diffusion through this highly viscous lava explains the lack of crystal growth. Obsidian is hard, brittle, and amorphous; it therefore fractures with sharp edges. In the past, it was used to manufacture cutting and piercing tools, and it has been used experimentally as surgical scalpel blades. 

Obsidian is mineral-like, but not a true mineral because as a glass it is not crystalline; in addition, its composition is too variable to be classified as a mineral. It is sometimes classified as a mineraloid. Though obsidian is usually dark in color, similar to mafic rocks such as basalt, obsidian's composition is extremely felsic. Obsidian consists mainly of SiO₂ (silicon dioxide), usually 70% or more. Crystalline rocks with a similar composition include granite and rhyolite. Because obsidian is metastable at the Earth's surface (over time the glass becomes fine-grained mineral crystals), no obsidian has been found that is older than the Cretaceous period. This transformation of obsidian is accelerated by the presence of water. Although newly-formed obsidian has a low water content, typically less than 1% water by weight, it becomes progressively hydrated when exposed to groundwater, forming perlite.

Pure obsidian is usually dark in appearance, though the color varies depending on the impurities present. Iron and other transition elements may give the obsidian a dark brown to black color. Most black obsidians contain nanoinclusions of magnetite, an iron oxide. Very few samples of obsidian are nearly colorless. In some stones, the inclusion of small, white, radially clustered crystals (spherulites) of the mineral cristobalite in the black glass produce a blotchy or snowflake pattern (snowflake obsidian). Obsidian may contain patterns of gas bubbles remaining from the lava flow, aligned along layers created as the molten rock was flowing before being cooled. These bubbles can produce interesting effects such as a golden sheen (sheen obsidian). An iridescent, rainbow-like sheen (fire obsidian) is caused by inclusions of magnetite nanoparticles creating thin-film interference. Colorful, striped obsidian (rainbow obsidian) from Mexico contains oriented nanorods of hedenbergite, which cause the rainbow striping effects by thin-film interference. 

[en.wikipedia.org]

Reported Benefits

• The holder of this stone will experience the effects of a more confident self and a boost in self-esteem.
• This stone is abundant in forgiveness, blocking negativity, and healing properties.
• It is very useful for removing anger, depression, and despair from oneself through meditation practices.
• This peaceful stone assists in protecting and balancing one's energy.
• It is a stone of love and light that helps one rid themselves of aggravation, bitterness, and resentment.
• This soothing stone contributes to one's personal growth through it's secure and protecting energy.
• Rainbow obsidian is a good assistant for dealing with melancholy while also reducing mood swings.
• Assists in guiding the owner of this stone in the appropriate direction.
• This stone is associated with sensitivity and compassion and has been known to unclog energy blockages or dams.
• It will help one realize that holding onto grudges and anger is completely unnecessary and will lead to only awful results.

LORE

• The many colors of this stone are combined to provide grounding that energizes and cleanses one's aura.
• This stone is effective in bringing the possessor to a closer understanding of the third dimension through manifestation.
• It is very good for any form of karmic cleansing as it provides an amplified life force to those who use it correctly.
• Benefits for diseases including intestinal tract, stomach, arthritic, and muscle issues have been reported throughout history.
• Aids in bringing the soul closer to conscious understanding as it helps one find light at the end of the tunnel.
• This stone's ability as an anti-inflammatory and pain relieving source have been proclaimed.
• It has been revered to bring wealth through it's energies of abundance and prosperity.
• Rainbow obsidian has been known to make break-ups and other negative feelings associated with relationships milder.
• This stone is known for aligning one's Chakras and cleansing the soul.

Historical Figures Who Used Rainbow Obsidian

• Pliny the Elder.
• John Dee.