Crystal
A crystal is a solid in which atoms are arranged in a neat, repeating three-dimensional pattern.
A crystal is any solid whose atoms line up in a regular pattern that repeats again and again in every direction. That hidden order often shows on the outside as flat faces and sharp edges, as in a cube of salt or a quartz point. Even when no faces are visible, the inside of a mineral grain is still crystalline.
In meteorites, crystals grew in several ways: from hot gas in the cloud around the young Sun, from cooling molten rock, from heated rock that slowly recrystallised, and even from water seeping through asteroids. The size of a crystal is a clue to how fast it formed. Tiny crystals usually mean rapid cooling, as in many chondrules, while the huge metal crystals seen in iron meteorites took millions of years to grow inside cooling asteroid cores.
You can see crystals in a meteorite with a hand lens: the glassy green grains in a pallasite are single crystals of olivine.
Related terms
Level: Beginner Ages 7 and up