Earth to Class

Key ideas -- Minerals, Rocks, and Resources

Minerals are solid, inorganic, crystalline substances with definite chemical compositions.

Minerals properties include: crystal shape, hardness, cleavage, fracture, color, luster, streak, density, and special properties, such as reaction to acid, salty taste, magnetism, and fluorescence.

Minerals properties depend upon their internal arrangement of atoms.

The silicon-oxygen tetrahedron is the building block of all the silicate minerals and has a pyramid shape.

Quartz (SiO2, silicon dioxide) is the most common mineral. Sand is mostly quartz and window glass is usually made of quartz

Other mineral groups include the oxides, carbonates, sulphides, halides, and native elements.

Rocks are solid mixtures composed of minerals.

Monominerallic rocks made of only one mineral and are rare. Most rocks are polymineralic, made of two or more minerals combined physically (not chemically).

Rocks are classified according to their origin (how they were formed.)

Igneous rocks formed through melting and solidification/crystallization. This produced a random pattern of intergrown crystals or, with very rapid cooling, a glassy appearance. Fossils are very rarely found in igneous rocks.

Igneous rocks with a coarse texture consisting of large (easily visible) crystals probably cooled slowly underground. They are sometimes called plutonic. Two examples are granite and gabbro.

Igneous rocks with a fine texture (barely visible crystals) cooled faster on the surface. They are called volcanic. Two examples are basalt and rhyolite. Pumice and obsidian are volcanic rocks that solidified so rapidly that no crystals could grow, so they have a glassy texture..

Basalts form most of the ocean crust, underlying almost three-quarters of the surface.

Sedimentary rocks form in several ways. Some form by compaction and cementation of sediments or rock fragments. Others form by chemical reactions, often in seawater. Most fossils are fond in sedimentary rocks.

Clastic sedimentary rocks are often classified by their grain size, from shale through sandstones and conglomerates. They are the most common rocks on the continent's surface. But they are really a thin veneer above non-sedimentary rocks forming most of the continental crust.

Sedimentary rocks can also form by chemical reactions to produce precipitate rocks, such as limestones and dolostones, and evaporites such as rock salt and rock gypsum.

Metamorphic rocks are created by changing pre-existing rocks under intense heat and pressure.

Some metamorphic rocks, exhibit banding or foliation.

Relationships among the various rock types can be represented by a diagram of the Rock Cycle.

All of the resources used to manufacture our everyday world come from some rock or mineral. Ores are extracted from the Earth by mining and refining processes.

Some ores are renewable and will replenish themselves in a short time, but most resources are non-renewable. Therefore, it is important to conserve or recycle.

Many common materials used in buildings and streets--such as bricks and concrete--are really 'artificial' sedimentary rocks. Window glass is really an 'artificial' igneous rock.

Gems are rare and beautiful minerals, and include diamonds, rubies, and sapphires.

Minerals and rocks form the basis for almost everything you use each day, from toothpaste to computers.