251. Crystals (29:27)
- Minerals are combinations of the elements of the earth. They can be identified by luster, color, hardness, specific gravity, density and cleavage, and by their crystal form. This program will deal with these forms. When the minerals solidify in cavities without interference with solid substances, they usually assume shapes which are characteristics of each particular mineral. To a physicist the crystal arrangement describes the internal arrangement of atoms. To the amateur observer the large well-formed crystals are beautiful examples of symmetry in nature. Some crystals are angular, others are then and needle-like; some dendritic or branching like limbs of a tree; others botryoidally or grapelike. You will see some common crystal forms: quartz, feldspar, mica, obsidian, garnet, magnetite, hematite, fluorite, calcite, dolomite, pyrite, gypsum, sugar, and salt.