Show AGATE AND ONYX the distinction between agate and onyx i ignot antt ap parent apparent to everyone ai as is indicated by the samples of the two minerals received by the united states geological survey with requests for information onyx marble or mexican onyx is composed of calcium carbonate or banded limestone true agate is a variety of silica onyx marble is much softer than agate and is rarely used for gems but when onyx is obtained in pieces of sufficient size it is cut and polished for small ornamental objects like inkstands ink stands and paper weights as well as for table tops and soda water fountains |