A Level Geology Eduqas

Rocks and minerals

Rocks and Minerals Overview

• Rocks are comprised of minerals, which are naturally occurring, inorganic solids that have a specific chemical formula and defined crystal structure.
• Minerals have physical properties that can be used for identification, including: colour, lustre, streak, hardness, cleavage, fracture and crystal shape.
• Rocks are classifiable as igneous, sedimentary, or metamorphic, based largely upon their formation processes.
• The rock cycle illustrates the transitions between these three rock types: igneous rocks convert to sedimentary rocks through weathering and erosion, which can then become metamorphic rocks through intense heat and pressure. This cycle can be repeated.

Igneous Rocks

• Igneous rocks are formed from the solidification of magma or lava.
• They may be intrusive (formed within the earth’s surface, such as granite) or extrusive (formed on the earth’s surface, like basalt).
• These rocks can be distinguished by their texture, classified as coarse-grained, fine-grained, or glassy.
• Common igneous rocks include granite, basalt, and pumice.

Sedimentary Rocks

• Sedimentary rocks are formed through the accumulation and compaction of sediments.
• They are classified into clastic, chemical, and organic, depending on the type of sedimentation process.
• Features like stratification, fossils, and ripple marks can typically be found in sedimentary rocks.
• Well-known examples are limestone, sandstone, and shale.

Metamorphic Rocks

• Metamorphic rocks originate from existing rocks, which are transformed by high temperature or pressure but do not melt.
• They are categorized as contact (caused by heat) or regional (due to pressure) metamorphic rocks.
• Telling features can include foliation, a layering due to pressure.
• Common examples include slate, marble, and gneiss.

Significance of Rocks and Minerals

• Rocks and minerals are significant for understanding the Earth's history, exploring for natural resources, and predicting the potential for natural hazards.
• Studying rock strata can provide information about past climates and events, as well as chronological data for geologic history.
• The exploration for oil, natural gas, and minerals relies on understanding the geological principles related to rocks and minerals.
• Measurement of rock and mineral properties can indicate the likelihood of earth activities such as earthquakes and volcanic eruptions.