Rainbow Obsidian
SpiritRock Shop
Museum Specimens
Rainbow Obsidian
“The various colors of obsidian are a result of several factors. Clear varieties of obsidian contain very few opaque
impurities or microscopic mineral crystals. Red or brown obsidian generally results from tiny crystals or inclusions
of hematite or limonite (iron oxide). Abundant, microscopic crystals of minerals like magnetite, hornblende,
pyroxene, plagioclase and biotite, combined with tiny fragments of rock, likely produce the jet-black varieties of
obsidian. Microscopic crystals of various types of feldspars may yield the unique blue, green, purple or bronze
colors associated with rainbow obsidian. The reflectance of rainbow obsidian is likely attributed to a preferred
orientation of microscopic crystals of feldspar or mica oriented along flow layers.
A certain amount of water always is present in obsidian. Very small inclusions of water vapor in the form of
bubbles often are trapped in the glass. Tiny gas bubbles that have been stretched nearly flat along the flow layers
in obsidian generally cause the reflectance of gold sheen and silver sheen obsidian. Some of these bubbles are
visible to the naked eye. The bubbles can be seen readily with a strong magnifying glass or a microscope.
Obsidian is relatively unstable from a geologic perspective. It is rare to find obsidian older than about 20 million
years, which is very youthful in comparison to most continental rocks that form the Earth's crust. Over a long
period of time, obsidian gradually changes from glass to rock in a process known as "devitrification." In this
process, the silica molecules within the glass slowly rearrange into organized crystal patterns. The "snowflakes" in
snowflake obsidian are quartz crystals that have formed through devitrification of the original obsidian. The
crystals that develop through devitrification cause obsidian to lose its conchoidal fracture and glassy texture.”

information source courtesy of...http://volcano.oregonstate.edu/obsidian

Obsidian is relatively soft with a typical hardness rating of 5 to 5.5.  Obsidian, unlike crystals, has no regular
structure and therefore fractures in smooth conchoidal (curved) shapes. Quality Rainbow Obsidian is in high
demand for making jewelery and artistic carvings and displays.

The Nevada, Utah and California area, referred to as the Great Basin, is an ideal location to find
Obsidian. There are a myriad of colors, patterns and mixes of Obsidians, making them a very
desirable collector item.
Click on any photo to see a larger version
Official PayPal Seal
Item # OBSR05139874
XXL Grade AA Polished
Dome Rainbow Obsidian
Display Specimen

XXL Grade AA Polished Dome Rainbow Obsidian Display
(photographed dry in its natural state)

This specimen weighs 7 lbs 6 oz or 7.4 pounds (3350g)
and measures 10.2 x 5.5 x 3.2 inches (26.3 x 14.1 x 8.2cm)

This piece has outstanding sheen and impressive natural sunlight viewing! (sheen seen at correct viewing
angle determines cutting or polishing angles) This is one of the strongest Rainbow Obsidians we have run
across. This piece has brilliant color displays of purple, blue, bronze and light green. We procured it in
Nevada, it is from Utah. Photos were taken outdoors in natural sunlight.
Be very Careful handling Obsidian. It is one of the sharpest known
glass like substances in the world!