8th Grade Earth Science
Chapter 3 Key Terms
Section 1
1. Cleavage: a mineral’s ability to split easily along flat surfaces
2. Crystal: a solid in which the atoms are arranged in a pattern that repeats again and
again
3. Fracture: the way a mineral looks when it breaks apart in an irregular way.
4. Inorganic: not formed from living things or the remains of living things
5. Luster: the way a mineral reflects light from its surface
6. Mineral: a naturally occurring, inorganic solid that has a crystal structure and a
definite chemical composition
7. Mohs hardness scale: a scale ranking ten minerals from softest to hardest; used in
testing the hardness of minerals
8. Streak: the color of a mineral’s powder
Section 2
1. Crystallization: the process by which atoms are arranged to form a material with a
crystal structure
2. Geode: a hollow rock inside which mineral crystals have formed.
3. Lava: liquid magma that reaches the surface; also, the rock formed when liquid lava
hardens
4. Magma: the molten mixture of rock-forming substances, gases, and water from the
mantle
5. Solution: a mixture in which one substance is dissolved in another
6. Vein: a narrow deposit of a mineral that is sharply different from the surrounding
rock
Section 3
1. alloy: a solid mixture of two or more elements, at least one of which is a metal
2. Gemstone: a hard, colorful mineral that has a brilliant or glassy luster and is valued
for its appearance
3. Ore: rock that contains a metal or economically useful mineral
4. Smelting: the process by which ore is melted to separate the useful metal from other
elements