ASTERIA

asteria, or star-stone (from gr. [greek: astaer], star), a name applied to such ornamental stones as exhibit when cut _en cabochon_ a luminous star. the typical asteria is the star-sapphire, generally a bluish-grey corundum, milky or opalescent, with a star of six rays. (see sapphire.) in red corundum the stellate reflexion is less common, and hence the star-ruby occasionally found with the star-sapphire in ceylon is among the most valued of "fancy stones." when the radiation is shown by yellow corundum, the stone is called star-topaz. cymophane, or chatoyant chrysoberyl, may also be asteriated. in all these cases the asterism is due to the reflexion of light from twin-lamellae or from fine tubular cavities or thin enclosures definitely arranged in the stone. the _astrion_ of pliny is believed to have been our moonstone, since it is described as a colourless stone from india having within it the appearance of a star shining with the light of the moon. all star-stones were formerly regarded with much superstition.