Comment: 05:04 - 06:08 (01:04)
Source: Annenberg/CPB Resources - Earth Revealed - 12. Minerals: The Materials of Earth
Keywords: mineral, quartz, orthoclase, olivine, plagioclase, "rock forming mineral", rock, geology
Our transcription: Over 2,000 varieties of minerals on Earth have been identified, and new ones are still being discovered.
But most are rare, including some that have only been found at a single location on the planet.
In fact, the common types of minerals number only about 200.
Examples include quartz, olivine, orthoclase and plagioclase.
These common mineral varieties are called rock forming minerals because they comprise most of the rocks on earth and also serve as the basis for classifying them.
Of course, before a rock can be classified, its minerals must be identified.
This is one of the most fundamental tasks in all of geology.
Geology School Keywords