MICROLITE

Mi″cro‐lite (?), n. [[Micro- + -lite.]] (Min.) 1. 1. A rare mineral of resinous luster and high specific gravity. It is a tantalate of calcium, and occurs in octahedral crystals usually very minute.
2. 2. (Min.) A minute inclosed crystal, often observed when minerals or rocks are examined in thin sections under the microscope.