1. Gemstones are commonly found in pegmatites, which are igneous rocks that are ____________.
a. exceptionally mafic
b. extrusive, forming from lava
c. exceptionally coarse grained
d. exceptionally fine grained
2. Cleavage in minerals refers to ____________.
a. a tendency to break in an irregular pattern
b. a tendency to break along planes of weakness
c. the sharpness of edges between crystal faces
d. the development of distinct crystal faces.