Lesson 7: What are Crystal Systems and Mineral Habits?


Step 1: Introduction to Gemology

Lesson 7

In crystallography, mineral habits refer to the way crystals form within a specific mineral. In the article, “How Gems Are Classified,” I mentioned that, at the molecular level, diamond looks like two pyramids attached at their bases and quartz has six sides. These are examples of “mineral habits” or “crystal systems.”

How Are Crystal Systems Defined?

There are six crystal systems. All minerals form crystals in one of these six systems. Although you may have seen more than six shapes of crystals, they’re all variations of one of these six habits. Each system is defined by a combination of three factors:

  • How many axes it has.
  • The lengths of the axes.
  • The angles at which the axes meet.

An axis is a direction between the sides. The shortest one is A. The longest is C. There is a B axis …

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