Chapter 10 Minerals, Rocks and Soils

Explain how society’s needs led to developments in technologies designed to use rocks. Classify and describe rocks based on their method of formation: sedimentary, igneous, metamorphic Explain various ways in which rocks can be weathered: mechanical, chemical Classify minerals based on their physical characteristics.

Minerals: naturally occurring inorganic solid materials, composed of one or more elements Rock: is a mixture of one or more minerals.

Most minerals are quite rare. Only a few are common (ex: quartz & mica) MicaQuartz

A mineral can be an element (a pure substance) or a compound (two or more substances). Some minerals are found in the earths crust (the outermost layer – this is where we live).

Granite is a type of rock that is made up of 4 different minerals. It is made up of quartz, feldspar, mica and hornblende. Granite is commonly found in the base of statues and in kitchen countertops (once it’s polished).

1) Hardness (Mohs Hardness Scale) 2) Shape 3) Lustre 4) Colour 5) Streak 6) Cleavage & Fracture

Frederick Mohs developed a scale in 1812 of ten minerals with a “hardness” value of This scale is used to identify different minerals based on its “scratchability”.

MineralMineral HardnessHardness of Common Objects talc1 (softest)Soft Pencil (1.5) gypsum2Fingernail (2.5) calcite3Piece of Copper (3.5) fluorite4Iron Nail (4.5) apatite5Glass (5.5) feldspar6Steel File (6.5) Quartz7Streak Plate (7) Topaz8Sandpaper (7.5) corundum9Emery Paper (9) diamond10

At times minerals appear as crystals. Crystals occur naturally and they have straight edges, flat sides and regular angles.

All of the minerals (approx 3000) can be found in 1 of 6 crystal shapes. ExamplesSystem Shape HaliteCubic WulfeniteTetragonal CorundumHexagonal TopazOrthohombic GypsumMonoclinic AlbiteTriclinic

Halite - Cubic

Wulfenite – tetragonal

Corundum – hexagonal

Topaz – orthohombic

Gypsum – monoclinic

Albite – triclinic

Lustre or “shininess” of a mineral depends on how light is reflected from its surface Example: Gold is a mineral that appears shiny while others such as talc appear dull Talc is a soft mineral. You can scratch it with your fingernail. It comes in many colors such as white, green, pink, and gray.

Color is one of the most attractive properties of minerals and offers clues into identifying them. Minerals are not always the same color all the time. For example, the mineral Corundum is white/clear when it’s pure but when there is iron and/or titanium in it, the color is blue (and is called sapphire). When it contains chromium it’s red (and is called a ruby).

Streak is the color that is left behind when a mineral is rubbed across a piece of an unglazed porcelain tile. For example: Gold leaves a yellow streak while pyrite (often called fools gold) leaves a greenish-black or brown-black streak. Minerals harder than 7 on Mohs Hardness Scale will not leave a streak

Cleavage and Fracture describe how the mineral breaks apart. If a mineral breaks along smooth, flat surfaces or planes it is said to have cleavage Mica is an example of a mineral with cleavage

Some minerals are so rare and beautiful that they are very valuable such as diamonds. Some common usages of diamonds: To make jewelry (rings, earrings, necklaces) On drill bits to cut through hard substances such as steel and rock Surgical scalpels, razor blades, dental drills and diamond coated computer parts

Your body needs over 20 different elements found in minerals to survive. For example iron helps the blood carry oxygen. Sodium (in small amounts) helps to regulate water in the body’s cells

When a mineral breaks apart with rough jagged edges it is said to have fracture Quartz is an example of a mineral with fracture