Chapter 3 Minerals Part II

How are Minerals formed? One way is the cooling of magma Atoms migrate together and form different compounds The elements present and the amounts determine the kind of minerals

How are minerals formed? Different crystal structures are formed at different temperatures If the magma cools slowly, large crystals are formed Heavier minerals such as magnetite sink and lighter ones float.

How are minerals formed? Minerals such as quartz and calcite form late in the cooling process and are known as hydrothermal minerals. In the last few years, hydrothermal vents have been formed on the ocean floor.

How are minerals formed? In these areas, sea water filters into the hot crust and is heated to 400 degrees C. The hot water then reacts with the crust and becomes a metal bearing liquid. When it returns to the cooler sea floor, it deposits minerals, including iron, copper and zinc sulfide.

Minerals from Solution When water is saturated with dissolved solids and can’t hold any more, the excess falls out of the solution. An example of this is the manganese nodules on the ocean floor

Minerals from Evaporation Minerals such as salt, gypsum and calcite (calcite forms in two ways) are formed from sea water when it evaporates. This happens in warmer parts of the world where the sun's heat evaporates the water and leaves the minerals.

Minerals from Weathering Chemical changes are caused by atmospheric oxygen, water and acid rain. Such action can change feldspars to kaolin and pyrite (fools gold) into a red-brown iron ore called iron pyrite (yellowboy)

Minerals from Metamorphosis Some minerals are formed when rocks are metamorphosed, that is subjected to heat and pressure Minerals formed in this way include garnet and mica.

Uses of Minerals Gems Rarity and beauty makes them valuable Gemstones used for jewelry are cut and polished and sometimes don’t resemble the raw form of the mineral

Gemstones May have a crystal structure that allows it to be cut in facets May have the addition of another mineral that gives it a brighter color

Ores A mineral is an ore if it contains a substance that can be sold for profit Hematite is the ore of iron Bauxite is the ore of aluminum Copper comes from chalcopyrite ore

Ores

Ore deposits are formed when fluids travel through weaknesses in rocks, such as fractures and cracks. The minerals dissolved in the fluids are left behind when the liquid evaporates, forming “vein deposits”

Mining Ores are only profitable if the cost of mining them is less than the value of the material being mined Waste rock has to be removed This can be expensive and harmful to the environment