A local or state natural-history museum can supply the address of the nearest society. These groups hold conventions at which individuals exhibit their collections, exchange specimens, and discuss every aspect of their hobby. Several simple tests are used to help identify the amateur collector's finds. The color of a piece of mineral is not always a dependable clue to its identity. Impurities, for example, affect color.
Pure quartz is colorless, but quartz occurs in many colors.
The green of malachite and the blue of azurite, however, are typical of these minerals. The streak test for color is made by rubbing the mineral on a piece of white unglazed tile. The rough surface of the tile grinds the edge of the mineral to a powder. The color of the powder may be different from that of the solid piece. Luster is another characteristic to be observed.