3 Unpolished Mineral Specimens. Each rock or mineral specimen measures approximately 1-2 inches in length along its longest side. Pegmatite is a holocrystalline (completely crystalline), intrusive igneous rock. With a basic composition similar to that of granite, Pegmatite tends to be composed of quartz, feldspar, and mica. It is made of interlocking phaneritic crystals that are typically bigger than 2.5cm (or 1 inch) in size. Those crystals are the most striking feature of pegmatites is their crystals, with individual ones having been found at over 10 meters in length. It is of economic importance, due to often containing rare earth minerals such as tin and tungsten, and gemstones like aquamarine, tourmaline, topaz, fluorite, apatite and corundum. Origin: CO, SD
