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.