Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
MINERALS S6E5.b Investigate the composition of rocks in terms of minerals. WHAT IS A MINERAL? • A mineral is a naturally formed, inorganic solid that has a definite crystalline structure. Let’s Break it Down!!! (FRAYER MODEL) • Naturally formed = made in nature/not “man-made”. • Inorganic = non-living • Solid = 3 dimensional, hard • Definite crystalline structure = made of two or more elements; forms crystals. CRYSTALS • Solid, geometric forms of minerals produced by a repeating pattern of atoms or molecules that is present throughout the mineral. How Many Minerals Have Geologists Discovered? • Geologists have discovered over 2,500. • However, we only see about 100 frequently. • Less than 20 are widely distributed. • 98.5% of the Earth consists of just eight elements. 8 Elements of the Earth 1) 2) 3) 4) 5) 6) 7) 8) Oxygen (46.6%) Silicon (27.7%) Aluminum (8.1%) Iron (5%) Calcium (3.6%) Sodium (2.8%) Potassium (2.6%) Magnesium (2.1%) Most Common Rock-Forming Minerals Quartz (SiO2) Calcite (CaCO3) Augite (Ca, Na) Hematite (Fe2O3) Micas Feldspars NATIVE ELEMENTS • A mineral that is composed of only one element. • Ex: gold & silver SILICATES vs. NONSILICATES • Minerals divided into 2 groups based on chemical composition • Minerals that contain a combination of silicon & oxygen are silicate minerals. • Silicate minerals make up more than 90% of the Earth’s crust. SILICATES vs. NONSILICATES • Minerals that do not contain a combination of silicon & oxygen are nonsilicate minerals. • Classes: native elements, carbonates, halides, oxides, sulfates, & sulfides. IDENTIFYING MINERALS • Color • Luster • Streak • Cleavage & Fracture • Hardness • Density • Special Properties COLOR • • • • What you see on the ouside! Not the best way to identify a mineral Same mineral can come in a variety of colors Ex: Quartz---purest state is clear; impurities can cause it to be different colors • Exposure to air & water can change color (Ex: pyrite---usually golden but changes to brown or black when exposed to air & water) LUSTER • Luster: the way a surface reflects light; whether a mineral is shiny or dull! • Metallic, submetallic or nonmetallic luster • Shiny = metallic luster • Reflective/dull = submetallic • Dull= nonmetallic luster STREAK • Streak: color of a mineral in powdered form • Rub mineral against a piece of unglazed porcelain (streak plate) • Mark left on streak plate is the streak. • Color of streak not always the color of the mineral sample. • Not affected by air or water • More reliable than color in identifying a mineral CLEAVAGE & FRACTURE • How a mineral breaks • Determined by arrangement of atoms • Cleavage: tendency to break along smooth, flat surfaces (Ex: halite & mica) • Fracture: tendency to break unevenly along curved or irregular surfaces (Ex: quartz) HARDNESS • Mineral’s resistance to being scratched • Mohs Hardness Scale • Ranges from 1 to 10; 1 being softest (talc) & 10 being the hardest (diamond) • Scratch tests; scientists use common items to test hardness. – – – – Fingernail has a hardness of 2-2.5 Knife blade is 3-4 Glass is 5-6 Steel file or nail is 6.5-7 A mineral of a given hardness will scratch any mineral that is softer than it is. DENSITY • The measure of how much matter is in a given amount of space. • Density is a ratio of an object’s mass to its volume • D=m/v • Measured in grams per cubic centimeter (g/cm3) DENSITY • Water has a density of 1g/cm3 • Used as a reference point for other substances. • Object sinks---it’s density is greater than 1g/cm3 • Object floats---it’s density is less than 1g/cm3 SPECIAL PROPERTIES • Some properties are particular to only a few types of minerals • Fluorescence, chemical reaction, optical properties, magnetism, taste, radioactivity