Presentation on theme: "GeoFacts Stalactites and other cave formations made from calcium carbonate take thousands of years to form. One estimate is that a stalactite will grow."— Presentation transcript:
GeoFacts Stalactites and other cave formations made from calcium carbonate take thousands of years to form. One estimate is that a stalactite will grow only 10 cm every 1000 years. MINERALS
What is a mineral? Five characteristics of all minerals: naturally occurring inorganic (was never alive) definite crystal structure (atoms arranged in an orderly pattern) solid specific chemical composition (made up of different elements and compounds) Earth’s crust is composed of about 3000 minerals.
Naturally occurring and inorganic… Minerals are formed from natural processes Any man-made mineral is called synthetic Minerals are inorganic because they are not alive and never were alive Salt is a mineral, but sugar is not. Sugar comes from plants. Coal is not a mineral because it forms over thousands of years from the buildup of dead/decaying matter.
Definite crystal structure The atoms in minerals are arranged in regular geometric patterns that are repeated. This regular formation is called a crystal
Solids with specific compositions Solids have definite shapes and volumes; liquids and gases do not. Many atoms have silicon and oxygen in them, but the arrangement and proportion of elements in these minerals are unique. The formula for quartz is SiO 2 The formula for pyroxene is MgSiO 3
Common elements found in minerals Eight elements make up 98.5% of the crust’s total mass: NameSymbol% by Mass OxygenO46.6 SiliconSi27.7 AluminumAl8.1 IronFe5.0 CalciumCa3.6 SodiumNa2.8 PotassiumK2.6 MagnesiumMg2.1
More than 90% of the minerals in Earth’s crust are compounds containing OXYGEN AND SILICON, the two most abundant elements. Most minerals are compounds. Quartz is a compound of silicon and oxygen Galena is a compound of lead and sulfur A few minerals consist of single elements and are called native elements: Examples: silver, copper, sulfur and diamond
Rock-forming minerals There are 8 minerals that make up most of the rocks of Earth’s crust. They are primarily composed of the eight most common elements in Earth’s crust. Quartz, feldspar, mica, pyroxene Amphibole, olivine, garnet, calcite We’ll talk more about rocks next chapter
Structure of minerals
Identifying minerals Mineralogy – the study of minerals and their unique properties Minerals are RARELY identified by one single property
Mineral properties Color – not the most reliable characteristic; minerals change color with a change in temperature, pressure or metal
Mineral properties Luster – describes how minerals shine in natural light We classify minerals as having metallic or non-metallic luster. Not all metallic minerals are metals!! We further classify using words such as vitreous, pearly, greasy, oily, dull, earthy
Mineral properties Streak – the color of a mineral’s powder; in many cases the streak will not be the same color as the mineral. The streaks of nonmetallic minerals are usually colorless or white
Mineral properties Hardness – resistance to being scratched Diamond is the hardest of all minerals. Talc is the softest of all minerals. The minerals in the table on the next slide were selected because they are easily recognized and are readily found in nature (except for diamond).
Mohs Scale of Hardness Friedrich Mohs devised a numeric scale that is used to express the hardness of minerals. You can determine the approximate hardness of any common mineral by using other common objects MineralHardnessComparison Talc1 Gypsum2Fingernail = 2.5 Calcite3Copper penny = 3.5 Fluorite4Iron nail = 4.5 Apatite5Glass = 5.5 Feldspar6Steel file = 6.5 Quartz7Streak plate = 7 Topaz8 Corundum9 Diamond10
Mineral properties Specific gravity – ratio of a mineral’s mass to the mass of an equal volume of water It tells you how many more times denser the mineral is than water.
Mineral properties Texture – the way a mineral feels This property is very subjective; a mineral may feel different to two people working together
Special properties HCl chemical test: look for bubbles to form Double refraction: shows a double image Fluorescence: the ability to glow under UV light Phosphorescence: the ability to glow in the dark Magnetism: attraction to magnets
Silica Tetrahedron More than 90% of the minerals in Earth’s crust are silicates. Silicon and oxygen bond in a way that forms a tetrahedron
Mineral groups Silicates – quartz and feldspar are the most common minerals found in this group Uses: gems, watches, potting soil additive Carbonates – calcite and dolomite are the most common minerals Uses: cement for construction, paper, medicines
Mineral groups Oxide – mineral that has oxygen combined with a metal element; hematite and magnetite are common minerals Uses: abrasives, plumbing fixtures, auto parts Sulfide – mineral that has sulfur combined with a metal element; pyrite (fool’s gold) and galena are common minerals Uses: jewelry, ores for manufacturing
Mining for minerals
Ores and mines Ore – minerals that contain useful substances that can be mined for a profit The classification of a mineral as an ore can also change if the supply of or demand for that mineral changes. Ores that are located deep within Earth’s crust are removed by mining Consequence of mining???
Gems Some minerals are rarer than others and are therefore classified as expensive gems. Gems – valuable minerals that are prized for their rarity and beauty Rubies and emeralds are more expensive than diamonds.