题目内容

Smoky quartz is the quartz contains trace amounts of:

Al
B. Fe
Ca
D. Mg

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The silicate minerals are the most common type of minerals. What's the percentages do they account for of Earth's crust?

A. Less than 50%
B. About 50%
C. More than 90%
D. Less than 10%

The crystals of magnetite are:

A. Cubes
B. Octahedrons
C. Dodecahedrons

The crystals of fluorite are:—crystals are cubes

A. Cubes
B. Octahedrons
C. Dodecahedrons

How many cleavage/cleavages is/are the mica has/have?

A. 1
B. 2
C. 3
D. 4

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