geology & minerals - geode mineral samples

agate amethyst barite calcite chalcedony chemicals collection color colorful colors colour crosssection crystal crystalline crystallization crystals cut dolomite earth geode geodes geologic geological geology igneous inorganic inside isolated jasper kaolinite layer limonite material millerite mineral mineralogical mineralogy mineraloids minerals nature nodules oxides polished polycrystalline pyrite quartz rock rocks sample samples section shell silicate slice smithsonite specimen sphalerite stone strunz surface syngenetically vesicles volcanic