This specimen is an example of a typical mineral that formed in a simple pegmatite environment.
Simple Pegmatites: Typical Minerals
Magma cools and crystallizes in a complex manner. During late stages in cooling the last magmatic fluids often crystallize into an exceptionally coarse-grained igneous rock called granite pegmatite. Pegmatites of granitic composition are the most common; minerals with large-sized crystals typically formed in such an environment are quartz, potassium feldspar (microcline and orthoclase), and muscovite and biotite mica.
Rye, New York