LITHOSPHERE

ROCKSMINERALS

SOIL

Lithosphere

The outer "solid" part of Earth. It has two parts, the crust and the

upper mantle. It is about 100 km thick.

Minerals

To be classified as a true mineral, a substance must be a solid and have a crystalline structure.

It must also be a naturally occurring, homogeneous substance with a defined chemical composition

Minerals: Inorganic solids and their composition and properties are defined

Classification of Minerals

1. Color2. Luster3. Hardness4. Streak

Color

Idiochromatic Idio “particular” Mineral in which the

color is due to some essential constituent of the stone, Eg, Malachite (Green)

and Almandine (deep red).

Allochromatic Allo “other” Mineral in which the

color can vary, due to possible impurities

Eg, Beryl (Aquamarine or Emarald)

Eg, Smoky Quartz or Amethyst (Quartz)

Luster

The way its surface reflects light. Minerals with a metallic luster: shiny,

opaque appearance similar to a bright chrome

Non-metallic lusters: shiny, but somewhat translucent or transparent lusters (glassy, adamantine), along with dull, earthy, waxy, and resinous lusters, are grouped as non-metallic.

Hardness

The Mohs scale of mineral hardness characterizes the scratch resistance of various minerals through the ability of a harder material to scratch a softer material.

Created in 1812 by the German mineralogist Friedrich Mohs

Streak

The color of a mineral when it is powdered is called the streak of the mineral.

Streak can be determined for any mineral by rubbing the mineral across the surface of a hard, unglazed porcelain material called a streak plate.

The streak and color of some minerals are the same. For others, the streak may be quite different from the color, as for example the red-brown streak of hematite, often a gray to silver-gray mineral.

Rocks

Heterogeneous solids composed of many minerals.

In general rocks are of three types, namely, igneous, sedimentary, and metamorphic.

Formed from volcanic eruptions

Classification

Igneous rocks : when molten magma cools

Volcanic or extrusive rocks result from magma reaching the surface as lava.

Classification

Sedimentary rocks : by deposition of either organic matter or chemical precipitates, followed by compaction of the particulate matter.

Sedimentary rocks form at or near the Earth's surface.

Classification

Metamorphic rocks: by subjecting any rock type to different temperature and pressure conditions than those in which the original rock was formed.

These temperatures and pressures are always higher than those at the Earth's surface and must be sufficiently high so as to change the original minerals into other mineral types or else into other forms of the same minerals (e.g. by recrystallisation).