This is a Glossary of terms you will find frequently used as you learn about your crystals. It also includes my own “spell it, sound it out” pronunciations. Not exactly dictionary proper, but it works. Be warned, you could develop a temporary Southern accent.
Adularescence (Ad jewel er essence) Adularescence is an optical phenomena often called the “moonstone” effect. The phenomenon is applied to feldspar, usually Orthoclase. When cut as a cabochon, it exhibits a floating, billowy bluish or white light as the stone is turned. Referred to as schiller by mineralogists. Less intense or ‘mild Adularescence’ occur more as a general scattering of light. This results in a slightly hazy or milky appearance in otherwise non-hazy stones. It is very frequently seen in common opal and rose quartz.
Asterism (ASS ta riz em) is an optical effect which appears as a star shape within a crystal. The Star-effect or “Asterism” is caused by the dense inclusions of tiny fibers of Rutile (also known as “silk”). The stars are created by the light reflecting from needle-like inclusions of Rutile aligned perpendicular to the rays of the star.
Crystals that exhibit this type of effect include: Star Rubies, Star Sapphires, Star Garnets, Star Rose Quartz, Star Diopside, Star Moonstone and Star Opal.
Aventurization (Ah VEN chur rize ation) is the colorful play of glittering reflections of small, leaf like inclusions on an opaque background. The inclusions could be hematite and/or goethite in the case of Aventurine Feldspar or fuchsite and/or hematite in the case of Aventurine Quartz.
Chatoyancy (sha TOY an see) “In gemology, chatoyancy (aka chatoyance or cat’s eye effect), is an optical reflectance effect seen in certain gemstones. Coined from the French “œil de chat,” meaning “cat’s eye,” chatoyancy arises either from the fibrous structure of a material, as in Tiger’s Eye, or from fibrous inclusions or cavities within the stone, as in cat’s eye Chrysoberyl.
The effect can be likened to the sheen off a spool of silk. The luminous streak of reflected light is always perpendicular to the direction of the fibers. For a gemstone to show this effect best, it must be cut en cabochon, with the fibers or fibrous structures parallel to the base of the finished stone.”
Concentric (con SIN trick) Concentric means having the same center, Think of the ripples you see when you throw a rock into a stream. The circles that form out from the center (where the rock landed) are what is known as concentric. Many Agates show concentric type rings.
Concretion (con CREE shun) A Concretion is a concentration of mineral growth around a nucleus within a sedimentary environment.
Mochi Marbles (Moqui Balls) are a great example of Concretion. The outer shell is hematite (iron oxide) and the inner nucleus is sandstone.
Crazing (Cray zing) is a condition that causes internal or surface cracks. Opal, Amber and Garnets can often be seen with this condition. It also can be seen on ceramics and other pottery items.
Photograph courtesy of Etsy.com
Fluorescence (floor ESS ence) is the temporary emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted light has a longer wavelength, and lower energy, than the absorbed radiation.
Iridescence (Ear ah des cents) is the play of color often seen when a light source hits a crack, internal fracture or flaws, resulting in the colors of a rainbow. Commercially, in the case of Fire and Ice Quartz, the effect is artificially created producing cracks in rock crystal.
Labradorescence (Lab bra door essence) is the play of color in metallic hues, especially in Labradorite and Spectrolite. Blue, gold and green effects are most common but the entire spectrum can be observed. The cause of the schiller is the interference phenomena of twinned layering.
Opaque (oh-PAY-k) When you are working with material that is impenetrable to visible light, it is called “Opaque”. Any crystal/mineral that is held up to a light source and no light passes through, leaving it unchanged in appearance is defined as Opaque. Blood stone would be an example of Opaque.
Semi-Transparent (Semi Trans PEAR ent) Semi Transparent is the effect when light is able to move through the piece in some areas which appear more transparent than other areas of denser material. Many semi-translucent pieces appear as if a sheer fabric is being held up in front of them. You can somewhat see through the fabric, but the light allowed through is lessened making the piece appear more clouded and muted.
Translucent (trans LOO cent) permitting light to pass through but diffusing it so that persons, objects, etc., on the opposite side are not clearly visible.
Example: frosted window glass is translucent but not transparent.
Transparent (trans PEAR ent) The definition of Transparent is the property of allowing transmission of light through a material. These pieces are the best to view internal inclusions like mists and veils or phantoms. Think of clear or see through.
This glossary is a perfect cheat sheet for beginners and advanced alike. Have a term you want to know more about? Contact me!