Crystalline Aggregates

268. The greater part of the specimens or masses of minerals that occur may be described as aggregations of imperfect crystals. Many specimens whose structure appears to the eye quite homogeneous, and destitute internally of distinct crystallization, can be shown to be composed of crystalline grains. Under the above head, consequently, are included all the remaining varieties of structure among minerals. The individuals composing imperfectly crystallized individuals may be: 1. Columns, or fibers, in which case the structure is columnar or fibrous. 2. Thin lamina, producing a lamellar structure. 3. Grains, constituting a granular structure.