Introduction to Minerals

Objectives Define mineral. Compare the two main groups of minerals. Identify the six types of silicate crystalline structures. Describe three common nonsilicate crystalline structures.

Introduction to Minerals

Why study minerals Made and remade on Earth’s surface, oceans, and in the layers inside of Earth. They give us insight into Earth’s historical development and dynamics. Essential to industry Iron, copper, aluminum and magnesium

Why study minerals? Important to economy Environmental Impacts Cost of rare to find “gem quality” minerals High cost Environmental Impacts Extraction of minerals

Minerals Seen in our daily lives. Many of you have already used a mineral today. Toothpaste Mica – sparkles Car Hematite – iron ore – steel (skyscrapers also) Makeup (especially shimmer and glitter) Mica and talc

Rarity Some minerals are rare and highly prized for their characteristics. Gold – conductivity, resistance to corrosion, high luster. Diamonds – Beauty and hardness Some minerals are very common. Quartz - sand

What is a mineral? Nutritionist – things to be eaten Add plant and animal life processes. Jeweler – a stone to be cut or polished. Geologist – a naturally occurring, inorganic compound with a fixed chemical composition and an orderly internal arrangement of atoms (IAOA).

Characteristics of Minerals mineral a natural, usually inorganic solid that has a characteristic chemical composition, an orderly internal structure, and a characteristic set of physical properties. To be a mineral, a substance must have four characteristics: it must be inorganic—it cannot be made of or by living things; it must occur naturally—it cannot be man-made; it must be a crystalline solid; it must have a consistent chemical composition.

Characteristics of Minerals You can tell whether an object is a mineral by asking four questions. Is it a nonliving material? Is it a solid? Does it have a crystalline structure? Is it formed in nature?

Characteristics of Minerals, continued The diagram below shows the four characteristics of minerals.

Crystalline Structure Each type of mineral is characterized by a specific geometric arrangement of atoms, or its crystalline structure. crystal a solid whose atoms, ions, or molecules are arranged in a regular, repeating pattern One way that scientists study the structure of crystals is by using X rays. X rays that pass through a crystal and strike a photographic plate produce an image that shows the geometric arrangement of the atoms in the crystal.

How is a crystals shape determined? Internal arrangement of atoms. The arrangement of atoms is determined by the atoms of the minerals. DEFINITE CRYSTAL STRUCTURE! Minerals can be grouped into crystal classes or systems.

Crystal Systems Isometric – Cubic – look like blocks Pyrite Tetragonal – 4 sided pyramids, prisms Zircon Hexagonal – 6 sided pyramids, prisms Beryl, quartz

Crystal Systems Orthorhombic – short and stubby Topaz Monoclinic – short and stubby with tilted faces at each end. Gypsum Triclinic – sharp flat edges, no right angles Feldspar

Mineral Structure To understand what a crystalline structure is, you need to know a little about the elements that make up a mineral. Elements are pure substances that cannot be separated or broken down into simpler substances by chemical means. 92 different elements Represented by one or two letter symbols O = Oxygen Si = Silicon

Atoms and Compounds Atoms and Compounds Minerals may be either elements or compounds. A compound is a substance made of atoms of two or more different elements joined by chemical bonds. Example: Halite (NaCl) Na is sodium Cl is chloride

Kinds of Minerals The 20 most common minerals are called rock-forming minerals because they form the rocks that make up Earth’s crust. Ten minerals are so common that they make up 90% of Earth’s crust. These minerals are quartz, orthoclase, plagioclase, muscovite, biotite, calcite, dolomite, halite, gypsum, and ferromagnesian minerals. All minerals can be classified into two main groups— silicate minerals and nonsilicate minerals —based on their chemical compositions.

Kinds of Minerals, continued Silicate Minerals silicate mineral a mineral that contains a combination of Silicon (Si) and Oxygen (O) and that may also contain one or more metals. Common silicate minerals include: quartz: the basic building block of many rocks Feldspars: minerals that are the main component of most rocks on Earth’s surface Micas: minerals that separate easily into sheets when they break ferromagnesian minerals, such as amphiboles, pyroxenes, and olivines. Silicate minerals make up 96% of Earth’s crust. Quartz and feldspar alone make up more than 50% of the crust. Crystalline Structure is made up of some arrangement of: 4 oxygen atoms 1 silicon atom

Silicate Minerals Crystal Structure yields a silicon oxygen – tetrahedron.

Kinds of Minerals, continued Nonsilicate Minerals nonsilicate mineral a mineral that does not contain compounds of silicon and oxygen Nonsilicate minerals comprise about 4% of Earth’s crust. Nonsilicate minerals are organized into six major groups based on their chemical compositions. The six major groups of nonsilicate minerals are carbonates, halides, native elements, oxides, sulfates, and sulfides.

Classes of Nonsilicate Minerals A mineral that is composed of only one element is called a native element. Gold and silver are examples of native elements Made up of only ONE element – other examples of native elements are: Copper – Cu Iron – Fe Diamond – C Native elements are used in communications and electronics equipment

Classes of Nonsilicate Minerals Carbonates are minerals that contain combinations of carbon and oxygen in their chemical structure Calcite and Dolomite are examples of Carbonates Used in cement, building stones, and fireworks.

Classes of Nonsilicate Minerals Halides are compounds that form when fluorine, chlorine, iodine, or bromine combine with sodium, potassium, or calcium. Fluorite and Halite are examples of Halides Halide minerals are used in the chemical industry and in detergents.

Classes of Nonsilicate Minerals Oxides are compounds that form when an element, such as aluminum or iron, combines chemically with oxygen. Corundum is an example of an Oxide. Oxide minerals are used to make abrasives, aircraft parts, and paint.

Classes of Nonsilicate Minerals Sulfates are minerals that contain sulfur and oxygen, SO4 . Gypsum/Selenite is an example of a Sulfate Sulfates are used in cosmetics, toothpaste, cement, and pain.

Classes of Nonsilicate Minerals Sulfides are minerals that contain one or more elements such as lead, iron, or nickel, combined with sulfur. Galena is an example of a Sulfide. Sulfide minerals are used to make batteries, medicines, and electronic parts.

Reading Check What compound of elements will you never find in a nonsilicate mineral? Nonsilicate minerals never contain compounds of silicon bonded to oxygen.