Glossary

• 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.