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1 Chapter 3-1 Minerals Study Guide Ms. Grady Minerals – → A mineral is a naturally occurring, inorganic solid that has a definite chemical composition and crystal structure. A mineral has an orderly arrangement of atoms. Summary of Characteristics of Minerals Naturally occurring Inorganic Solid Definite chemical composition Ex, halite →NaCl Crystal Structure Pattern of atoms repeated *Naturally = not artificial or synthetic Minerals or Not??? Yes , No, Minerals not minerals ICE Petroleum – not a solid so no. GOLD Tree trunk – No, it was living so no. DIAMOND Orange Juice – not a solid so no TALC Seashells – No because they are organic QUARTZ Granite – no because it is a rock not a mineral. Properties used to identify minerals Crystal structure Hardness Color Luster Specific Gravity (density) Streak Cleavage or fracture Special properties *Inorganic = not organic – not made by life processes. *Composition = make up/formula *Atom = tiny particles that make up matter (composed of protons, electrons, and neutrons) Every mineral has an orderly arrangement of atoms and a definite chemical composition which gives it a unique set of physical properties. The crystal form is the external expression of a mineral’s orderly arrangement of atoms. There are 4,000 minerals on Earth. Crystalline means that atoms are arranged in a pattern that is repeated over and over again. Only a solid can be a mineral. Ex. An Opal is not a mineral because it atoms are Not all solids are minerals. not all arranged in a definite, repeating pattern (even though it is a naturally occurring, inorganic solid). 2 Crystal = a solid which the atoms are arranged in orderly, repeating patterns. A crystal system is a group of crystals Crystals form by many processes. that have similar atomic arrangements and similar external crystal shapes. Ex. 1 – crystals that form from magma Ex. 2 – crystals that form from solutions of salts. Ex. hexagonal, tetragonal, and cubic. Example: Because the rose quartz crystals developed in a The rose quartz has atoms arranged in tight space. repeating patterns but you can’t see the crystal shape on the outside of the mineral. Why? → The clear quartz crystals developed in freely in an open space. 3 Crystals from Magma Naturally processes form minerals in many ways as mentioned above. When magma cools slowly then the crystals Magma Hot melted rock material which cools when it that form are usually large enough to see reaches Earth’s surface or even when it is with the eye. trapped below the surface.→ Why? Because atoms have enough time to move together and form into larger crystals. When magma cools rapidly (quickly), the crystals that form will be small and you can’t easily see the individual mineral crystals. Crystals from Solution Crystals can form from When water evaporates, (as one might see minerals dissolved in in a dry climate like Nevada or water California) ions that are left behind can come together to form crystals. An example of this is the halite 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. Minerals can form from a solution in this way without the need for evaporation. Located in Death Valley, California 4 Mineral Compositions and Groups 90 elements occur naturally in Earth’s crust. Most of Earth’s crust is composed of 8 elements. Oxygen(most abundant/plentiful) Silicon (most abundant/plentiful) Aluminum Iron Calcium Sodium Potassium Magnesium Most of the rock forming minerals belong to a Silicates = minerals that contain silicon and group called the silicates.→ oxygen and usually one or more other elements. Oxygen (O) and Silicon (Si) are 2 elements that form the basic building blocks of most of minerals in Earth’s crust and mantle. Feldspar = silicate Quartz = silicate Calcite = carbonate All of these are examples of rock-forming minerals. Feldspar Quartz Calcite 5