Adamantine Luster Adamantine is the term used to describe the luster exhibited by diamonds and gems with a Refractive Index of 1.9 – 2.5. The root word adamant derives from the Greek word adamastos which means untameable. Throughout history the word adamant has...
Adularescence Adularescence is an optical phenomena often called the “moonstone” effect. The phenomenon is applied to feldspar, usually orthoclase that, when cut as a cabochon, exhibits a floating, billowy bluish or white light as the stone is turned. Referred to as...
Aggregate Aggregate in the geologic or gemologic sense of the word, is defined as a composition of various materials (usually mineralogical and chemical) brought together by processes within the earth to form rock. A famous example of an aggregate is Lapis...
Alexandrite-Like Alexandrite-like refers to the ability of a gem material to change colors when viewed under different light sources such as daylight and incandescent lighting. It is named after the natural “change of color” gemstone alexandrite which is a variety...
Allochromatic The term allochromatic is used in reference to gem materials that derive their color from elements that are not an essential part of their chemical composition. In other words, the gemstone’s color is due to impurities. A good example of an...
Alluvial Alluvial means ‘deposited by water’. The word ‘alluvial’ is derived from the Latin word ‘alluvius’, from ‘alluere’, which means ‘to wash against’. When rocks are exposed to the elements they can...
