Pegmatites in Maine often contain such minerals as beryl, tourmaline, lepidolite, apatite, quartz, and garnet. Plutonic Rocks have cooled and solidified at some depth and much more slowly. Plutonic rocks include granite, diorite, gabbro, and peridotite or pyroxenite. These are course-grained and composed of common primary mineral such as quartz, feldspar, mica, and dark mineral. Sedimentary Rocks form when wind, water and ice break down rock formations, carry them off, and deposit them in layers where they pile up thicker and thicker, gradually forming rigidly cemented masses.
Feldspars change to clay, metals dissolve in water.
Sedimentary rocks include arkose, conglomerate, breccia, sandstone, shale, limestone, dolomite, salt and coal. These are low temperature minerals banded, stratified, and often fossiliferous. Metamorphic Rocks are formed by the pressure and heat that accompany deep burial of sedimentary rocks creating an environment like the original one deep under the crust or in volcanoes. Moisture, oxygen and carbon dioxide are forced out and the sediments making up the shale, sandstone, or limestone begin to change. For example, the clay of shales will revert back to the original feldspar and mica, become metamorphosed or changed.