Beautiful Australian Opals

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About Opal
Getting Started
Base Color
Consistency and Directionality
Cut, Inclusions and Weight
Fire Color
Doublets and Tripletts
Fire Pattern
Glossay of Terms
Natural, Synthetic, Etc
Myths and Legends
Opal Books
Opal Care
Opal Evaluation
Opal Pricing
Some Large and Famous Opals
Types of Opals

Glossary of Terms

  • Agate - Fine-grained variegated chalcedony with banded, striped, or mosslike coloration.
  • Amorphous - Having no definite form.
  • Black Opal - Rare form of mineral opal found only in Australia.
  • Cabochon - A gem or bead cut in convex form and highly polished but not faceted. Also, this style of cutting.
  • Crazing - Tiny cracks on the surface.
  • Crystal Opal - Transparent with flashes. Highly valued due to the brilliance of its colors and the fact that many layers of color within the stone can also be seen.
  • Crystalline - Composed of or resembling crystals.
  • Direction - A measure of opal value.
  • Dopping - Attaching a gem to a wooden extension by means of adhesive wax in order to polish or facet the stone with greater ease.
  • Doublet - A manufactured opal gem consisting of two layers: Opal and obsidian or ironstone.
  • Fire (or pinfire) - A measure of an opal's color or iridescence.
  • Fire Opal - A translucent or transparent mineral opal found mainly in Mexico.
  • Geothermal - Of or relating to the heat of the Earth's interior.
  • Mohs' Scale - A scale of hardness for minerals in which 1 represents the hardness of talc and 10 (sometimes 15) represents the hardness of diamond.
  • Organic Opal - An opal formed from the chemical petrifying of organic materials such as wood or seashells.
  • Potch - Crusty mineral coating on naturally occurring opals.
  • Quartz - A mineral SiO2, silicon dioxide, that occurs in crystals or crystalline masses.
  • Silica - A mineral SiO2, silicon dioxide, that occurs in crystalline or amorphous masses.
  • Synthetic Opal - Man-Made gem opal.
  • Triplet - A manufactured opal gem consisting of three layers: Clear quartz, opal, and obsidian or ironstone.White Opal - common form of gem quality opal, usually whit or milky white in color with bright pinfire flashes.
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