Rocks & Minerals Test

Luster

The way a mineral reflects light, categorized as metallic or nonmetallic.

Streak

The color of a mineral when it is powdered; often more reliable than surface color.

Hardness

A measure of a mineral's resistance to scratching, assessed using tools like a fingernail or glass.

Cleavage

The tendency of a mineral to break along flat planes.

Fracture

The irregular or curved breakage of a mineral, not along flat planes.

Density

The mass of a mineral per unit volume, often used for identification.

Magnetism

The property of attracting or repelling certain materials, helpful in mineral identification.

Acid Reaction

A mineral's response to acid, indicated by fizzing if carbonates are present.

Intrusive

Igneous rocks formed from slow cooling magma beneath the Earth's surface, resulting in coarse texture.

Extrusive

Igneous rocks formed from fast cooling lava at the Earth's surface, typically fine-grained.

Felsic

A composition of igneous rocks that are light-colored and high in silica.

Mafic

Igneous rocks that are darker in color and rich in iron and magnesium.

Clastic Sedimentary Rocks

Rocks formed from the accumulation and lithification of fragments of pre-existing rocks.

Grain Size

A classification criterion for sediments and sedimentary rocks, indicating particle diameter.

Sorting

A measure of the uniformity of grain sizes in sediment, indicating the energy of transportation.

Foliation

The alignment of minerals within a metamorphic rock, indicative of pressure during metamorphism.

Superposition

A principle stating that in undisturbed sedimentary rock layers, the oldest layer is on the bottom.

Cross-Cutting Relationships

Geological principle that states that an intrusion or fault is younger than the rocks it cuts through.

Bowen’s Reaction Series

A sequence that explains the order of mineral crystallization from cooling magma.

Fractional Crystallization

A process where early formed crystals are removed from the melt, changing the composition of the remaining liquid.

Index Fossils

Fossils used to identify and date the specific time frame of the rock in which they are found.

Contact Metamorphism

Metamorphism that occurs when rocks are heated by nearby molten rock.

Regional Metamorphism

Metamorphism that occurs over large areas due to heat and pressure.

Sedimentary Structures

Features in sedimentary rocks, such as fossils and mud cracks, that provide insights into the depositional environment.

Mineral Identification

The process of identifying minerals using multiple properties such as hardness, streak, and luster.