Geology: Rocks vs Minerals

Rocks vs Minerals

• Rocks are different from minerals, but both are solids and can be found in the earth's crust.
• Minerals are naturally occurring substances with unique chemical and physical properties.
• Minerals are inorganic, multicolored, have a specific structure, and are defined by their chemical composition.
• Minerals have a definite crystalline structure and can have nutritional value.

Mineral Definition

• Minerals are inorganic uniform chemical compositions of a solid that have a crystalline internal structure and occur naturally.
• Minerals can be made from multiple types of elements or just one.
• Minerals can be vast, like the size of a tree, or very small, like a grain of sand.
• Salt or NaCl is an example of the crystalline structure of minerals.

Classifying Minerals

• Minerals are classified by their chemical composition and crystalline structure.
• Other ways to characterize minerals include examining the color, density, hardness, streak, luster, and solubility.
• Geologists classify crystal structures by the number of sides, angles, cleavage, and fracture.
• There are three main types of crystalline structures: Body-Centered Cubic (BCC), Hexagonal Close-Packed (HCP), and Cubic Close-Packed (CCP).

Rock Definition

• A rock is a solid interconnected collective of two or more crystalline minerals.
• Rocks are usually made up of various types of mineral grains, held together in one solid form, and can be large or small.
• The study of rocks is called petrology.
• Rocks do not always have a repeating arrangement of atoms like minerals do.

Classifying Rocks

• Rocks are classified based on how they are formed.
• There are three main rock classifications: igneous, sedimentary, and metamorphic.
• Rocks are made through the rock cycle, which either creates new rocks or recycles old rocks.

Igneous Rocks

• Made from hot magma that cools to create rock.
• Emerges from volcanoes.
• The quicker it cools, the finer the grain texture; the slower it cools, the larger the grain texture.
• Can be intrusive or extrusive.

Sedimentary Rocks

• Made over time by pressure from other rocks.
• Shows fossil records.
• Used to interpret history.

Metamorphic Rocks

• Made from other rocks.
• Chemical reactions can alter the minerals.
• Different levels of heat can create different rocks from the same minerals.

The Rock Cycle

• The process in which all rock is made or recycled.
• Igneous → Sedimentary: through weathering, sedimentation, and lithification.
• Sedimentary → Metamorphic: through heat & pressure, deformation and recrystallization.
• Metamorphic → Igneous: through melting and crystallization.

Is a Rock a Mineral?

• A rock is not a mineral, and minerals do not always make rocks.
• Most rocks are made of minerals, but some rocks have no minerals.
• Rocks that contain minerals: granite, shale, limestone, marble, sandstone, coal.
• Rocks that do not contain minerals: peat, chalk, flint.