Gem Library

BUYER’S OVERVIEW:
Opal is considered to be a semi-precious gemstone and while somewhat limited in nature, clear, large, natural stones are available. The Opal’s entrancing play of colors beguiles gemstone enthusiasts the world over and while the neon greens, blues and reds found in the choicest stones simply cannot be overlooked, not all opals are the same, stones that exhibit deep rich reds and have strong play of color are the most valuable. Opals love (and need) to be worn a lot as this enables the stone to maintain its water balance. Opals absorb moisture from the wearer’s skin and from the air.

COLOR:
Opal can exhibit almost any color against a background ranging from white through brown to a dark gray or black.

APPEARANCE:
Transparent to opaque.

Phenomena:
Opal exhibits play-of-color.

SIZE RANGE:
From melee (0.01) to 100 carats; large specimens are available.

TYPICAL CUTTING STYLES:
Transparent: faceted and beads
Translucent to opaque: cabochons, beads and carvings.

POSSIBLE ENHANCEMENTS & TREATMENTS:
Opals can be enhanced with wax, plastic, smoke and carbonized sugar. These treatments are common and stability ranges from fair to excellent. Cleaning care needs to be given to all treatments as most can be removed with any form of chemical cleaning.

HARDNESS:
5 to 6½ on the Mohs scale.

BEST USE OF THE GEMSTONE:
Opal is not a strong gemstone and as such, earrings, pendants, pins, and tie tacks are probably the safest choice for this stone. Rings should be limited to occasional wear and the stones should be set with a protective setting. Avoid rough handing.

CARE & CLEANING:
It is best to never expose colored gemstones to cleaning solvents or chemicals of any kind. Opals love to be worn a lot as this enables the stone to maintain its water balance. Opals absorb moisture from the wearer’s skin and from the air.
Common cleaning methods include:
Ultrasonic: never
Steamer: never (very heat sensitive)
Warm soapy water: safe
Reaction to Chemicals: can be damaged by acids.
Reaction to Heat: very heat sensitive, heat will destroy play-of-color and cause gem to crack.
Stability to Light: like all opals, it should not be exposed to intense light over long periods.

INTERESTING FACTS ABOUT THIS GEMSTONE:
The name Opal comes from the Greek word, “Opallos”, meaning “to see a change of color”. Opal is a form of non-crystalline silica gel that was formed millions of years ago as water seeped over silica bearing rock and pooled in crevices and cracks in the sedimentary rock. In 1963 it was discovered that Opal is composed of minute spheres of silica in closely packed arrangements. Spheres in a regular pattern produce the best display of play-of-color as light passes through the transparent spheres and is scattered by the voids between the spheres. Small spheres produce violet, indigo, blue and green, the large spheres produce red and orange with red being the rarest color.

Australia produces about 90% of the worlds Opal, including some of the exciting newer colors such as blue and pink. Fire Opal comes from Mexico and Brazil, often found in the rock strata near many extinct volcanoes, typically in cavities and crevices dotting the canyon walls. Fire Opal is so highly regarded in Mexico that it has been named the national gemstone. The U. S. produces a small amount of Opal but a significant percentage of the material is not stable and tends to dry out and crack.



DESIGNATION:
Opal is the birthstone for October and the gemstone for the 14^th wedding anniversary.

GEM LORE