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What is a Mineral? • It is a naturally occurring , inorganic solid, with a specific chemical composition and a definite crystalline structure Pyromorphite What do all minerals have in common? All: 1. Are formed by natural processes. 2. Are NOT alive and NEVER were alive (INORGANIC) 3. Have a definite volume and shape (hard solid) 4. Are elements or compounds with a unique chemical makeup 5. Are made up of particles that are arranged in a pattern that is repeated over and over (called a CRYSTAL) How minerals form? • They are four major processes by which minerals form: 1. Crystallization of magma. 2. Precipitation 3. Changes in pressure and temperature. 4. Formation from Hydrothermal solutions. Crystallization from Magma • When the magma as liquid cools to a solid state, then forms crystals. • Size of crystals depends on • 1) the rate at which the magma/lava cools. • 2) the amount of gas the magma/lava contains, • 3) the chemical composition of the magma/lava Precipitation • The water in Earth’s lakes and rivers beneath its surface contains many dissolved substances. When the water evaporates , some of dissolved materials can react to form minerals. Pressure and Temperature • An increase in pressure can cause a mineral to recrystallize while still solid. • Changes in temperature can cause certain minerals to be unstable. Under these conditions, new minerals can be formed. Hydrothermal solutions • It is a hot mixture of water and dissolved substances. They have temperature about 100 -300 C. Ex: Sulfur minerals , Bornite Watch Classifying Minerals Clip Mineral Groups in the Earth’s Crust Minerals that form the rocks within Earth’s crust belong to Seven (7) main mineral groups: ( we will focus on the first three) 1) Silicates 2) Carbonates 3) Oxides 4) Sulfaes 5) Halides 6) Sulfides 7) Native Hints to Classify Mineral Groups A Mineral groups that end with “ate” and have an oxygen group in its chemical formula are one of the following; Silicates = Si + Ox Olivine (Mg,Fe)2SiO4 Barite BaSO4 Sulfates = S + Ox Carbonates = C + Ox Calcite CaCO3 Mineral Groups 1 Silicates ) Silicon and oxygen are the most common elements in earth’s crust. A mineral group that has silicon and oxygen as part of their atomic structure. The most dominant mineral class is the silicates. Comprise more than 96% of the crust. All silicate minerals have the same building block: Silicon-Oxygen Tetrahedron - consisting of four oxygen ions (negative) surrounding one small silicon ion (positive), forming a tetrahedron, a pyramid shape with 4 identical faces. Mineral Groups 1 Silicates ) Mineral Groups 1 Silicates ) Rock forming Silicates are divided into two (2) groups: Simatic Silicates (Ferromagnesium) rich in silicon and magnesium (Iron). main rock type found in the ocean floor and comprise less than 15% of the crust. mineral are dark in color. Mineral Groups 4 Oxides compounds consisting of an atomic structure of oxygen ) combined with one or more metals. most common oxides are those of iron (Fe2O3) and aluminum (Al2O3), referred to as Ore - Minerals. 5 Halides ) compounds consisting of an atomic structure of chlorine or fluorine with sodium, potassium, or calcium. Halite (NaCl) is the most common halide. Often referred to as table salt. Mineral Groups 6 Sulfides compounds consisting of an atomic structure of one ) or more metals combined with sulfur. common ore mineral. (FeS2), Galena (PbS), Sphalerite (ZnS). Examples: Pyrite 7 Native Minerals ) elements that occur uncombined in nature. commonly called native elements. Examples: (Au), Silver (Ag), Copper (Cu), & Sulfur (S) Gold