Minerals

Building Blocks of Matter An element is a substance that cannot be broken down into simpler substances by chemical or physical means The basic unit of matter is the atom (smallest particle of matter that retains characteristics of an element) Atoms are made of subatomic particles: protons (+), electrons (-), and neutrons Protons (atomic number) and neutrons reside in the nucleus Electrons move around in energy levels outside of the nucleus

Building Blocks of Matter

Building Blocks of Matter Atoms of the same element but with different neutrons are isotopes Carbon-12, Carbon-13, Radioactive Carbon- 14

Building Blocks of Matter Two or more elements can combine to form compounds (H2O) Properties of compound differ from the elements Ionic bonds form between positive and negative ions (element loses or gains electron) Covalent bonds involve sharing of electrons between elements (H2O) Metallic bonds form when electrons are shared by metal ions

Building Blocks of Matter

Minerals Mineral is a naturally occurring, inorganic solid, with an orderly crystalline structure and a definite chemical composition Natural, not man-made (synthetic) Solid at normal Earth temperatures Crystalline- atoms or ions are arranged in orderly repetitive manner Consistent element (gold) or chemical compound (quartz [SiO2]) Inorganic

How Minerals Form Crystallization from magma as it cools Precipitation occurs when water evaporates leaving the dissolved substances can react to form minerals Changes in pressure and temperature can cause atoms to rearrange Hydrothermal solution (water and dissolved substances between 100C-300C) form new mineral when come in contact with mineral

Mineral Groups Minerals are classified based on their composition Silicates are composed primarily of silicon and oxygen Make up 95% of all minerals on Earth Ferromagnesian minerals contain a lot of the elements iron and magnesium (usually dark in color) Nonferromagnesium silicates are usually light in color because they don’t contain iron and magnesium

Mineral Groups Sulfides have compounds combined with sulfur Galena (PbS), sphalerite (ZnS) Carbonates have compounds made up of a carbon atom and bordered by oxygen Halides contain elements that combine with halogen ion (chlorine, fluorine, bromine, iodine) Salt is a halide mineral called halite

Mineral Groups Sulfates contain compounds made of sulfur enclosed by four oxygen atoms (CaSO4) Oxides contain element combined with oxygen Hematite (rust) Native elements are elements in relatively pure form Gold (Au), Copper (Cu)

Properties of Minerals Mineral’s properties can help identify them Hardness is a mineral’s resistance to scratching Moh’s hardness scale ranges from 1-10 10 is diamond, talc is 1

Cleavage Cleavage is the breakage along planes of weakness (based on atomic arrangements) One direction: mica breaks into sheets because bond holding sheets together is weak Two directions: feldspar breaks into two directions at about 90 degrees Three directions: calcite, 75 degrees

Fracture and Streak Fracture occurs when minerals don’t show cleavage when broken Break along curved surfaces, splinter, or just break unevenly Streak is the color of the mineral in its powdered form Created by rubbing mineral across streak plate More reliable than color of mineral (small amounts of different elements can change color of mineral)

Color Sapphires have different colors based on small amounts of different elements

Luster and Crystal Form Luster describes how light is reflected from the surface of a mineral Metallic luster- have metallic appearance Glassy- quartz; earthy- chalk Crystal form is the visible expression of a mineral’s internal arrangement of atoms If allowed to form slowly and without space restrictions they form consistent crystal shape

Density and Acid Test Density is the ratio of an object’s mass to its volume (D=m/V) Density of a pure mineral is a constant value Adding dilute HCl to an unknown mineral is the acid test If the sample fizzes, it is a carbonate The fizz is carbon dioxide