Obsidian Value, Price, and Jewelry Information


OBSIDIAN: Mexico (banded and sheen varieties): Utah (“snowflake obsidian,” cabochon 30 x 40 mm). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Obsidian Value

The International Gem Society (IGS) has a list of businesses offering gemstone appraisal services.

Obsidian Information

DataValue
NameObsidian
Is a Variety ofNatural Glass
VarietiesApache Tears, Fire Obsidian, Mahogany Obsidian, Rainbow Obsidian, Sheen Obsidian, Snowflake Obsidian
Crystallography Amorphous; usually as rounded masses ejected in volcanic eruptions, as small broken pieces, fine, hairlike filaments (for example, Pele’s Hair), and as flows.
Refractive Index 1.48-1.51; usually 1.49
Colors Black; gray, banded with brown streaks. Iridescence noted: gold, silver, blue, violet, green, and combinations of these colors, due to inclusions of minute bubbles that reflect light.
Luster Vitreous.
Fracture Conchoidal (best example of this type of fracture). Very brittle. Basalt glass may be splintery, brittle.
Hardness 5; 6 for basalt glass.
Specific Gravity 2.33-2.42; 2.70—3.0 for basalt glass.
Birefringence Crystals included in obsidian may be birefringent.
Cleavage None.
Luminescence None.
Transparency Transparent to opaque
FormulaVariable composition: SiO2 approximately 66-72% + oxides of Ca, Na, K, and so forth. Basaltic glass is ~5O% SiO2.
Optics Isotropic. N
EtymologyAfter Obsius, an explorer who discovered this material in Ethiopia, according to the Ancient Roman naturalist Pliny the Elder.
OccurrenceObsidian is found in areas of present and former volcanic activity.
Inclusions Elongated, torpedo-shaped bubbles, round bubbles, teardrop-shaped bubbles. Bubbles are often in parallel arrangement. Needlelike inclusions may give a silvery sheen. Protogenic silica minerals crystallizing in obsidian may be white and resemble snowflakes, hence the term snowflake obsidian.
“Obsidian,” showing conchoidal fractures, by Kevin Walsh is licensed under CC By 2.0
“Obsidian,” showing conchoidal fractures, by Kevin Walsh is licensed under CC By 2.0

Comments

Obsidian is naturally occurring volcanic glass.  This material is considered a rock. It’s heat sensitive and brittle, so cutting requires great care. Faceted gems tend to be very dark, except in small sizes. These pieces make delicate jewelry.

Varieties

This attractive material has a wide variety of appearances.

Snowflake obsidian, with spherulites of cristobalite, is widely used in jewelry as beads and cabochons.

“Snowflake Obsidian” by James St. John is licensed under CC By 2.0
“Snowflake Obsidian” by James St. John is licensed under CC By 2.0

Apache tears, which are cores of unaltered glass in nodular shells of decomposed obsidian, are popular among beginning hobbyists. Some of these have been faceted.

“Apache Tears” by Stephanie Clifford is licensed under CC By 2.0
“Apache Tears” by Stephanie Clifford is licensed under CC By 2.0

Mahogany obsidian has a reddish-brown color due to iron impurities.

“Mahogany Obsidian” by James St. John is licensed under CC By 2.0
“Mahogany Obsidian” by James St. John is licensed under CC By 2.0

Rainbow and fire obsidian show multiple brilliant colors due to inclusions of magnetite nanocrystals. Fire obsidian contains thinner layers of magnetite than the rainbow variety.

“Fire Obsidian” by Jessa and Mark Anderson is licensed under CC By 2.0
“Fire Obsidian” by Jessa and Mark Anderson is licensed under CC By 2.0

Sheen obsidian has a sheen produced by inclusions of gas bubbles.

Obsidian has been knapped into arrowheads and other tools since prehistoric times. This material can be shaped into a blade with a cutting edge sharper than surgical steel. “(HMM) Ancient technology - a broken piece of obsidian stone tool” by aotoro is licensed under CC By 2.0
Obsidian has been knapped into arrowheads and other tools since prehistoric times. This material can be shaped into a blade with a cutting edge sharper than surgical steel. “(HMM) Ancient technology – a broken piece of obsidian stone tool” by aotoro is licensed under CC By 2.0

Pele’s Hair is a light, string-like volcanic basalt glass that can become airborne.

Pele's hair can be found caught in trees and outdoor structures. “Pele's hair (DSC_3905)” by Thomas Tunsch is licensed under CC By-SA 2.0
Pele’s hair can be found caught in trees and outdoor structures. “Pele’s hair (DSC_3905)” by Thomas Tunsch is licensed under CC By-SA 2.0

Synthetics

Artificial or manufactured glass in blue, green, or red is sometimes passed off as obsidian. Natural obsidian does not form in these colors.  (However, these colors can be shown through iridescence). See the glass gem listing for more information.

Sources

The United States is a major source of gem-quality material.

  • Oregon: fire, mahogany, and rainbow varieties are known.
  • Wyoming: notably at Yellowstone National Park.
  • New Mexico: Apache tears.
  • Arizona; Colorado; California; Nevada: several localities.
  • Utah: major source of snowflake variety.
  • Hawaii: Pele’s hair and other varieties
  • Mexico: abundant, especially banded and sheen varieties.
  • Ecuador; Iceland; Indonesia; Italy; Japan.

Stone Sizes

Fragments range from microscopic to many inches across. Carvings up to 8-10 inches could be made. Larger pieces are available in place in certain localities.

“Obsidian, black pendant, copper wire wrapped” by D Fredericks is licensed under CC By 2.0
“Obsidian, black pendant, copper wire wrapped” by D Fredericks is licensed under CC By 2.0