SF Fig. 7.10. (A) Quartz mineral
Image courtesy of JJ Harrison, Wikimedia Commons
Title
Compare-Contrast-Connect: Minerals and Rocks
NGSS Science and Engineering Practices
NGSS Crosscutting Concepts
NGSS Disciplinary Core Ideas
Table of Contents
Nomenclature and classification are very important in science. Being very precise about what you are investigating helps scientists communicate findings and results across geographic and cultural boundaries. Non-scientists commonly use the terms “mineral” and “rock” interchangeably in everyday language, but in science they mean very different things. The International Mineralogical Association describes a mineral as an element or chemical compound that is normally crystalline. Crystalline refers to the orderly geometric spatial arrangement of atoms in the mineral. Table salt or sodium chloride (NaCl) is a familiar mineral that forms cube-shaped crystals. Typically the chemistry and crystalline structure of a mineral help scientists to classify it. Minerals are formed as a result of geological processes.
An example of a mineral is quartz. Quartz is made up of a crystalline structure of the compound silicon dioxide, SiO2 (SF Fig. 7.10 A). By contrast, rocks are mixtures of minerals. The mixture may be homogenous or heterogeneous in nature. Homogeneous rocks are made up of more than one type of mineral, but are uniform throughout and usually one color. In heterogeneous rocks, the minerals are distributed unevenly, so they are often not uniform in color. Slate is an example of a homogeneous stone, with even mineral distribution and color. Granite is an example of a heterogeneous rock that contains a mixture of the minerals quartz, mica, and feldspar and is variable in color (SF Fig. 7.10 B).
SF Fig. 7.10. (B) Granite rock composed of a mixture of quartz, mica, and feldspar
Image courtesy of Friman, Wikimedia Commons
Question Set
- Using SF Table 7.3, identify each picture as either a rock or a mineral. Explain how you came to this conclusion.
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A. Diorite Image copyright and source
Image courtesy of Siim Sepp, Wikimedia Commons |
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B. Ametrine Image copyright and source
Image courtesy of Ra’ike, Wikimedia Commons |
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C. Kimberlite Image copyright and source
Image courtesy of Siim Sepp, Wikimedia Commons |
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D. Pyrite Image copyright and source
Image courtesy of Rob Lavinsky, iRocks.com |
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E. Aragonite Image copyright and source
Image courtesy of Didier Descouens, Wikimedia Commons |
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F. Obsidian Image copyright and source
Image courtesy of Ji-Elle, Wikimedia Commons |
