AIM: How are Minerals

Created?

Minerals can form in TWO ways:1. Crystallization of molten material2. Crystallization of materials dissolved in water.

Crystallization: when atoms are arranged to form a material with a crystal structure.

Minerals from Magma and Lava• Minerals form when hot magma cools inside the

earth, or when lava hardens on the surface.

• When these liquids cool to a solid state, they form crystals.

Video clip

• The size of the crystals depends on how fast the magma cools.– Magma deep in the ground cools SLOWLY, and crystals

can grow very large.– Magma close to the surface cools QUICKLY, and crystals

don’t have time to grow very large.

The minerals that make up basalt are the same as those that make up gabbro. Basalt forms when magma cools quickly, and gabbro forms when magma cools very slowly.

Basalt Gabbro

Minerals from Solution• A solution is a mixture in which one substance is dissolved

in another.

• Sometimes elements or compounds dissolved in water can leave a solution, and crystallization occurs.

Salt on a stone of the Dead Sea, Israel

Massive beams of selenite dwarf human explorers in Mexico's Cave of Crystals, deep below the Chihuahuan Desert. Formed over millennia, these crystals are among the largest yet discovered on Earth

1. Minerals formed by Evaporation• When a solution evaporates, minerals can be left

behind. – Example: Deposits of the mineral HALITE (salt) formed

over millions of years when ancient seas slowly evaporated.

– In the U.S., halite deposits are found in the Midwest, the Southwest, and along the Gulf Coast.

SEARLES LAKE, California

Salt deposits

2. Minerals from hot water solutions• Deep underground

magma can heat water and cause nearby minerals to dissolve.

• When the water begins to cool, the minerals will begin to crystallize.

Geodes are formations that occur in gas bubbles in sedimentary rock.

Hydrothermal forces bring silica solutions which crystallize into a quartz crystal cave, usually starting as tiny interlocked crystals or Agate, and finishing with an interior of larger single crystals or Quartz.

These can be many colors, Amathyst, Citrine, Smoky Quartz.

Tourmaline crystals form as magma cools deep beneath the surface

• A vein is a narrow slab of a mineral that is different from the surrounding rock.– Form when hot water solutions flow through cracks

within the surrounding rock.

Pure silver can crystallize in veins from hot water solutions.

A calcite vein within another rock.