Hardness: 6.00
Refractive Index: 1.37-1.47
Specific Gravity: 2.10
Birthstone: October
Astral Stone: Libra, Scorpio
Anniversary Stone: 14th
Origination: Australia
Care & Cleaning: Black precious opals should be stored in a separate area apart from other gems or metals that may scratch its surface. Do not wear your black precious opal in the presence of harsh chemicals and hot water. Always apply makeup, perfume and hair spray prior to wearing this most costly gem. A soft cloth with an optional dab of olive oil will preserve your black precious opal for many years.
Fiction, Facts & Folklore:
Any precious opal with a dark background of vivid color contrast is considered a black precious opal.
Opals not intense enough to categorize as black precious opals are known in the trade as �semi-black.�
High quality black opals will show an intense play of red. These opals sometimes fetch tens of thousands of dollars, and are considered by gem experts to be among the most prized and costly gems in the world.
Because it is such a costly gem, man has developed a synthetic black opal. This stone has failed to capture much of the market because even though it is synthetic, its cost is relatively high.
A more affordable option would be a black opal triplet, which essentially consists of a layer of clear quartz over a layer of white precious opal with a black background. This background can be dyed agate, although it is usually an adhesive.
For additional information, see �opal�.