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 O O O Si Si Si O O

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

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

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

Halite has a CUBIC crystal structure. 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)