 Chapter 3

What is a mineral ? - naturally occurring, inorganic solid with a definite composition and an orderly arrangement of atoms. There are about 4000 different minerals on Earth. All share five characteristics: They are: 1) Formed by natural processes. 2) Inorganic: are not, and never were, alive 3) Crystalline: atoms are arranged in a pattern that is repeated 4) Solid: definite volume and shape (gasses and liquids don’t have a definite shape) 5) All elements or compounds with a definite chemical composition. Structure of Minerals: (pg. 64) Structure of minerals are various forms of: Crystals: solid in which the atoms are arranged in a repeated pattern

 Crystals from Magma: › Magma – hot melted rock material that cools when it reaches the Earth’s surface. › As it cools, atoms lose heat energy, move closer together and combine into compounds. › These compounds arrange themselves into orderly, repeating patterns. › The size of the crystals that form depends on how rapidly the magma cools.  When magma cools slowly, crystals are large enough to see with unaided eye.  When magma cools rapidly, crystals will be small.

 Crystals from Solution: › Minerals dissolved in water.  When water evaporates, as in a dry climate, ions that are left behind can come together to form crystals. › If too much of a substance is dissolved in water, ions can come together and crystals of that substance can begin to form in the solution…no need for evaporation.

90 elements occur naturally in Earth’s crust. Approximately 98% of the crust is made of only 8 of these elements. Of the thousands of known minerals, only a few dozen are common, and these are mostly composed of the eight most common elements in Earth’s crust Silicates – are minerals that contain silicon (Si) and oxygen (O) and usually one or more other elements. Since silicon and oxygen are the two most abundant elements in Earth’s crust, these two elements alone combine to form the basic building blocks of most minerals. Chart on Pg. 66

Physical Properties : – Appearance: what does it look like? (can’t rely on this alone) – Hardness: measure of how easily a mineral can be scratched – Mohs Scale of Hardness: (pg. 69) – The scale lists the hardness of 10 minerals. Talc is the softest, has a hardness value of 1. Diamond is the hardest with a hardness value of 10. – If you have two minerals that look the same and you want to determine what each is, you can use this scale. – If you can scratch one of the minerals with a nail, but not a fingernail then you know that the hardness of the mineral is somewhere between 3 and 4

– Luster: describes how light reflects from the surface of the mineral Metallic or nonmetallic… shines like a metal or not? - Specific Gravity: the ratio of it’s weight compared with the weight of an equal volume of water…how heavy it is. – Color: color of mineral – Streak: color of the mineral when it is powdered… when you rub it across a surface, what kind of mark is left? – Cleave: when broken, mineral breaks along a smooth flat surface – Fracture: when broken, mineral breaks off with uneven rough surfaces

 Magnetic?  How light bends if shined through it?  Hydrochloric acid makes it fizz?

Uses of Minerals Gems: highly prized minerals (pg. 74) – - Special varieties of particular minerals – - They are brighter, clearer and more colorful than common minerals Diamonds: - very hard gem - Used as an abrasive and cutting tool Rubies: - used to produce a specific type of laser light Quartz: - used in electronics and as timepieces Ore: a mineral or rock that contains a useful substance that can be mined at a profit - Iron is an ore that is used from producing frying pans to ships Titanium: is a durable, lightweight, metallic element that comes from minerals. - used in golf clubs, racing bicycles, automotive body parts, aircraft, eyeglass frames and tennis rackets

Mineral Properties HardnessLuster Cleavage and Fracture Streak Specific Gravity