Michelangelo carved his statues from the metamorphic
rock, marble. Almost all of this material came from quarries near the
town of Carrara, Italy, so this rock is referred to as the "Carrara
marble." He would inspect the marble before he would work with it,
to insure that the rock would express his artistic genius.
Marble is composed of carbonate minerals, mainly
of calcite (CaCO3). The original rock is limestone, usually
derived from fossil shells. During metamorphism, the original fossils
and cement dissolve, and reform in place as new calcite crystals. Since
the crystals all form at about the same time, they are pretty close to
the same size. This gives marble a "sugary" appearance.
Marbles often contain small amounts of quartz,
mica, pyrite, or hematite. These often give a color to the marble. For
example, small amounts of hematite make the marble yellow-orange in