MINERALS MINERAL CHARACTERISTICS Mineral Natural occurring inorganic solid

MINERALS

MINERAL CHARACTERISTICS Mineral = Natural occurring, inorganic solid that has a crystal structure and a definite chemical composition.

MINERAL CHARACTERISTICS Naturally Occurring: § Formed by a process in the natural world § Mineral Quartz forms naturally as molten material cools and hardens deep beneath Earth’s surface.

MINERAL CHARACTERISTICS Inorganic: § Minerals cannot form from materials that were once part of a living thing. § For example, coal forms naturally in the crust, but it is not a mineral because it comes from the remains of plants.

MINERAL CHARACTERISTICS Solid: § Minerals are always solid. § They have a definite volume and shape.

MINERAL CHARACTERISTICS Crystal Structure: § Particles of a mineral line up in a pattern that repeats over and over again. § The repeating pattern forms a solid called a CRYSTAL. § Crystals have flat sides, that meet at sharp edges and corners.

MINERAL CHARACTERISTICS Definite Chemical Composition: § Minerals always contain certain elements in certain amounts. § Almost all minerals are compounds. § Some elements occur in nature in a pure form…like copper, silver, and gold. O Si O O O Si Si O O

IDENTIFYING MINERALS There are over 4, 000 minerals in our world! How do geologists identify all of them? ? ?

IDENTIFYING MINERALS Each mineral has characteristic properties that can be used to identify it: • • • Color • Cleavage and Streak Fracture Luster • Special Density Properties Hardness Crystal Systems

IDENTIFYING MINERALS Color: § The mineral malachite is always green and the mineral azurite is always blue. § No other minerals look quite the same as these! § Their color makes them identifiable.

IDENTIFYING MINERALS Color: § Color is easy to observe, but is not the best way to identify a mineral. § Which one is GOLD? Gold Chalcopyrite Pyrite (Fool’s Gold)

IDENTIFYING MINERALS Streak: § The streak of a mineral is the color of its powder. You can observe a streak by rubbing a mineral against a piece of unglazed porcelain tile.

IDENTIFYING MINERALS Luster: § Luster describes how light is reflected from a mineral’s surface.

Luster of Minerals Metallic Glassy Greasy or Pearly Earthy or Dull Silky Waxy

IDENTIFYING MINERALS Density: § Density is how much mass is in a given space (or volume). § Sometimes you can FEEL density by measuring the difference of the two minerals in your hand. § Density = Mass/Volume § To find the volume of a mineral: Place the mineral in water to determine how much water the sample displaces. The volume of the displaced water equals the volume of the sample.

IDENTIFYING MINERALS Hardness: § Friedrich Mohs, an Austrian mineral expert, invented a test to describe the hardness of minerals. § The Mohs Hardness Scale ranks ten minerals from softest to hardest.

IDENTIFYING MINERALS Mohs Hardness Scale 1 2 3 4 5 Talc Gypsum Calcite Fluorite Apatite 6 7 8 9 10 Feldspar Quartz Topaz Corundum Diamond

IDENTIFYING MINERALS Crystal Systems: § All minerals are crystal shaped § Minerals that have room to grow form complete, perfect crystals. § Minerals that grow in tight places form incomplete shapes. Halite has a CUBIC crystal structure.

IDENTIFYING MINERALS

IDENTIFYING MINERALS Cleavage and Fracture: § A mineral that splits easily along flat surfaces has the property called cleavage. § Most minerals do not split apart evenly. Instead they have a characteristic type of fracture. § Fracture describes how a mineral looks when it breaks apart in an irregular way.

IDENTIFYING MINERALS

IDENTIFYING MINERALS Special Properties: § Magnetism: Magnetite attracts metal like a magnet. § Fluorescence: Scheelite is a mineral that glows in ultraviolet light

IDENTIFYING MINERALS Special Properties : § Optical Properties: Calcite bends light to produce a double image. § Reactivity with Acid: Aragonite reacts chemically to acid.

MINERAL PROPERTIES LAB Luster Test: metallic, dull, or glassy? Streak Color Test: (use the streak plates) Hardness: (use the Moh’s hardness scale) Magnetic: (use the small magnet)