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.
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 and silicon dioxide that occurs in crystals or crystalline masses.
Silica- A mineral SiO2 and 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 that’s usually milky white in color with bright pinfire flashes.
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.
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 and silicon dioxide that occurs in crystals or crystalline masses.
Silica- A mineral SiO2 and 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 that’s usually milky white in color with bright pinfire flashes.
