Vocabulary for Investigation 4: Take It For Granite
1) Granite- an igneous rock that forms when Magma (molten
rock) cools deep in the Earth’s crust. It makes up about 22% of the
Earth’s crust. Its main ingredients are feldspar, quartz, black mica
and hornblende. Usually light in color, granite often has a saltand-pepper appearance because of the dark minerals sprinkled
throughout the lighter-colored minerals. In some areas granites
have a decidedly pink cast because of the color of feldspar. The
size of the crystals in a particular mass of granite depends on the
rate at which the magma cooled. The slower the cooling, the
bigger the crystals. Because of its hardness, it polishes well and is
popular for buildings and monuments.
2) Micas- range in color from black to almost colorless. Its most
interesting property is its cleavage; it pulls apart in paper-thin,
flexible sheets. Large, colorless “books” of mica were once used
for windows in stoves and ranges. It can be scratched wit a penny.
(Hardness = 2.5-3)
3) Feldspar- is not one mineral, but a group of related minerals.
Feldspars come in a variety of colors, including white, yellow,
pink, pale green, and blue. They are most abundant minerals in the
earth’s crust. They usually have a smooth, glassy or pearly luster.
Feldspars are the basis for clays, such as kaolin, and are used in the
manufacture of glazes, flux enamels and binders for the ceramics
industry. Feldspars cannot be scratched with a paperclip.
(Hardness = 6)
4) Hornblende- a member of a group of minerals called the
amphiboles. Its crystals are often long and needlelike and
sometimes appear fibrous. It is usually black but can also be dark
green or brown. It has a glassy luster. It splits apart into wedgeshaped pieces. Hornblende usually cannot be scratched with a
paper clip. (Hardness = 5-6)