Earth 17

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Minerals of the Earth’s Crust

mineral is a naturally occurring inorganic solid, with a definite chemical composition, and an ordered atomic arrangement. Minerals are naturally occurring. They are not made by humans. Minerals are inorganic. Minerals have specific properties that can be measured and compared: color, streak, hardness, cleavage, crystalline structure, transparency, tenacity, and magnetism.

Lesson 1 (or “Day 1”) Material
Lesson 2 (or “Day 2”) Material
Lesson 3 (or “Day 3”) Material
Lesson 4 (or “Day 4”) Material

3:47 Rocks and Minerals

1:32 M02-Mineral Identification – How to Identify Luster

(3:00) Earth’s Minerals



Compare Contrast and Debate

Research, compare and contrast Silicon (Si) coming from silicates and Aluminum (Al) coming primarily from bauxite.

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Special Notes and Notices

Instructor Emphasis:

  • Science & Engineering Practice: Engage in scientific argument from evidence.
  • Cross-Cutting Concept: Cause and Effect: Mechanisms and explanations.

Silicates are considered to be a mineral. The largest grouping of minerals by far are the silicates; most rocks are composed of greater than 95% silicate minerals, and over 90% of the Earth’s crust is composed of these minerals.  Silicon is a chemical element with symbol Si and atomic number 14. Over 90% of the Earth’s crust is composed of silicate minerals, making silicon the second most abundant element in the Earth’s crust (about 28% by mass) after oxygen.

Bauxite ore is NOT considered a mineral. Aluminum is the most abundant metal element in the Earth’s crust. Bauxite ore is the main source of aluminum and contains the aluminum minerals gibbsite, boehmite, and diaspore. .But, because bauxited is a mixture of minerals, bauxite itself is a rock, not a mineral.

An interesting (man-made) combination of the two is called Silumin. Silumin is a group of lightweight, high-strength aluminium alloys based on an aluminum–silicon system. Aluminium-silicon alloys contain 3 to 25% silicon content. Casting is the primary use of aluminum-silicon alloys, but they can also be utilized in rapid solidification processes and powder metallurgy. Alloys used by powder metallurgy, rather than casting, may contain even more silicon, up to 50%. Silumin has a high resistance to corrosion, making it useful in humid environments.


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