Brown spar or brown-spar is a trivial, partly obsolete name for at least four carbonate minerals that are relatively similar in composition: ankerite, dolomite, magnesite and siderite, which have a ch

Belomorite, sometimes peristerite, moonstone, murchisonite, Ceylon opal, or hecatolite, is a decorative variety of albite of white or light gray color with a distinct iridescence effect. By compositio