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Identifying and classifying the different types of rocks is not an easy task, but you can have some success by using the following clues as a starting point. **Reference document used in the Rocks and Minerals session during the EdGEO Teacher Workshop at GACMAC 2013. Presented by Mining Matters.**
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Source: 1. Deeper and Deeper: Discovering Rocks and Minerals, 2007, Mining Matters
2. Rock Star101: Introduction to Rocks, 2012, Minerals Ed BC
Identifying and classifying the different types of rocks is not an easy task, but
you can have some success by using the following clues as a starting point.
Sedimentary Rocks
Sedimentary rocks are formed from sediments or precipitation of crystals in waters at or
near Earth’s surface. The sediments are compacted and cemented when buried.
o Broken, rounded particles of varying sizes o Particles may originate from rock or minerals o Relatively soft and friable o Grains held together by mineral cement o Sometimes dull looking (not crystalline) o Layered at various scales o May contain fossils o May react with acid (fizzes) o May be crystalline (Chemical sedimentary rocks)
Igneous Rocks Intrusive (Plutonic) - Formed from molten rock; underground; cooled very slowly;, formed coarse mineral crystals.
o Coarse crystals o Grains you can see; speckled o Hard
Extrusive (Volcanic) - Formed molten rock or volcanic fragments at or near Earth’s surface; cooled quickly; formed fine mineral crystals.
o Grains too small to see with naked eye o Crystalline, sparkly o Trapped gas bubbles (vesicles)
o Hard (most)
Metamorphic Rocks Metamorphic rocks form from any type of pre‐existing rock subjected to high pressure and/or high temperature.
o Prominent layering defined by aligned minerals (banded, foliation)
o Crystalline, coarse or fine (sparkly)
o Wavy, irregular layering
o Very hard
Rock Discovery: Clues you can use
