Pegmatite is a felsic igneous rock that forms during the late stages of magma crystallization. These rocks are recognizable due to their large crystals and an abundance of different minerals. The most common minerals present in pegmatites like this sample are biotite, quartz and K-feldspar. Pegmatite is also well known for containing rare minerals and gemstones, depending on the temperatures and ions present during formation. Rare minerals that have been found in pegmatite samples include spodumene, beryl, tourmaline, topaz, and fluorite. Crystals in pegmatites are a minimum of 1 cm in diameter like in this sample and can grow up to several meters in much larger samples, the loonie in these images is present for scale. Large crystals can form due to superheating of water that is rich in dissolved ions. These ions are mobile in water and move freely, rapidly creating large crystals. Pegmatites grow at the margins of magma intrusions in zones called batholiths. The most common uses of pegmatites are as gemstones and construction material like decorative building facies or countertops.