The rock-forming minerals make up the bulk of most rocks in the
Earth’s crust.. There are almost 5,000 known mineral species, but the vast majority of rocks are composed of combinations of several common minerals called “rock-forming minerals.. Rock-forming minerals are: feldspar, quartz, amphiboles, mica, olivine, garnet, calcite, pyroxenes. These are important for geologists because they are the most common minerals.
To be considered a common rock-forming mineral, you need a mineral:
A) To be one of the most abundant minerals in the Earth’s crust;
B) being one of the original minerals present during the formation of a crusted rock; and,
C) Be an important mineral in determining the classification of a rock.