Matter and Minerals Matter Elements and the Periodic

Matter and Minerals

Matter Elements and the Periodic Table Elements are the basic building blocks of minerals. Over 100 elements are known.

Matter Atoms Smallest particles of matter Have all the characteristics of an element The nucleus is the central part of an atom and contains • protons, which have positive electrical charges • neutrons, which have neutral electrical charges

Matter Atoms Energy levels, or shells • surround the nucleus • contain electrons—negatively charged particles The atomic number is the number of protons in the nucleus of an atom.

Model of an Atom

Matter Isotopes of an element have the same number of protons but varying numbers of neutrons. Have different mass numbers: the sum of the neutrons plus protons Many isotopes are radioactive and emit energy and particles. The mass number is the number of neutrons and protons in the nucleus of an atom.

Matter Why Atoms Bond When an atom’s outermost energy level does not contain the maximum number of electrons, the atom is likely to form a chemical bond with one or more atoms. • A compound consists of two or more elements that are chemically combined in specific proportions. • An ion is an atom that gains or losses electrons.

Matter Types of Chemical Bonds 1. Ionic bonds form between positive and negative ions. 2. Covalent bonds form when atoms share electrons. 3. Metallic bonds form when metal ions share electrons.

Minerals: the building blocks of rocks • Definition of a Mineral: ü naturally occurring ü inorganic ü solid ü characteristic crystalline structure ü definite chemical composition

How do we identify minerals? • Physical properties: ü ü ü ü Color Luster Hardness Crystal shape Cleavage Specific gravity Other

Physical Properties of Minerals • Color: – Most obvious, but often misleading – Different colors may result from impurities Example: Quartz

Physical Properties of Minerals • Color: Streak – color of a mineral in powdered form (used for metallic minerals) Obtained by scratching a mineral on a piece of unglazed porcelain. Example: Hematite

Streak • Red chalk on a chalk board makes red marks. White chalk makes white marks. • Not all minerals work this way. When some minerals are scratched along a ceramic streak plate, it creates a different color.

Gold • When gold is run across a streak plate it makes a yellowish-gold color. • That makes sense.

Pyrite or “Fool’s Gold” • When pyrite is run across a streak plate, it has a black or dark green streak. • Pyrite is not worth much money, while gold is worth a lot. They look alike, so miners call it fool’s gold.

Hematite • Hematite’s color is grey, but its streak is red. • Hema means blood. • The mineral was named hematite because it looked like it was bleeding when it was taken across a streak plate.

One mineral property we will not use… COLOR

A mineral can be many different colors. Below is Mica.

Many minerals can be the same color. Below are gold colored minerals. Which one is gold?

The answer… None of them were real gold.

Just like with people… Outside color does not tell you much about the important characteristics.

Physical Properties of Minerals • Luster: – How a mineral surface reflects light – Two major types: • Metallic luster • Non-metallic luster Metallic example: Galena Non-metallic example: Orthoclase

Pyrite (Fool’s Gold) Displays Metallic Luster.

Physical Properties of Minerals • Hardness: – How easy it is to scratch a mineral – Mohs Scale of Hardness • relative scale • consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

Mohs Scale of Hardness Hardest (10) – Diamond Softest (1) – Talc Common objects: - Fingernail (2. 5) - Copper penny (3. 5) - Wire nail (4. 5) - Glass (5. 5) - Streak plate (6. 5)

Hardness • Is measured by how easy it is to scratch. • Geologists order the hardness by… 1. Scratched by a fingernail. 2. Scratched by a penny. 3. Scratched by a nail. 4. Scratched by a diamond. These are not all of the tools geologists use, but it will work for our experiment.

Gypsum is soft, it can be scratched by a fingernail.

Calcite is soft, but a little harder because it cannot be scratched by a fingernail, but it can be scratched by a penny.

Fluorite is harder. It can be scratched by a nail, but not a penny or fingernail.

Diamonds are the hardest mineral, so it scratches every mineral.

Physical Properties of Minerals • Crystal shape (or form): – external expression of a mineral’s internal atomic structure – planar surfaces are called crystal faces – angles between crystal faces are constant for any particular mineral Quartz Pyrite

Physical Properties of Minerals • Cleavage vs. Fracture: – The way a mineral breaks – Cleavage: tendency of a mineral to break along planes of weakness – Minerals that do not exhibit cleavage are said to fracture Do not confuse cleavage planes with crystal faces! Crystal faces are just on the surface and may not repeat when the mineral is broken.

Physical Properties of Minerals • Cleavage is described by: – Number of planes – Angles between adjacent planes – These are constant for a particular mineral

Physical Properties of Minerals • Cleavage (1 direction): Example: mica

Mica Has Cleavage in One Direction

Physical Properties of Minerals • Cleavage (2 directions): orthoclase amphibole

Physical Properties of Minerals • Cleavage (3 directions): halite calcite

Physical Properties of Minerals • Cleavage (4 directions): fluorite

Physical Properties of Minerals • Fracture: – minerals that do not exhibit cleavage are said to fracture – smooth, curved surfaces when minerals break in a glass-like manner: conchoidal fracture Quartz

Conchoidal Fracture

Physical Properties of Minerals • Specific gravity: – weight of a mineral divided by weight of an equal volume of water – metallic minerals tend to have higher specific gravity than non-metallic minerals Galena SG=7. 5 Quartz SG=2. 67

Physical Properties of Minerals • Other properties: – reaction with hydrochloric acid (calcite fizzes) – taste (halite tastes salty) – feel (talc feels soapy, graphite feels greasy) – magnetism (magnetite attracts a magnet)

Mineral Groups • Rock-forming minerals – ~30 common minerals make up most rocks in Earth’s crust – Composed mainly of the 8 elements that make up over 98% of the crust

Mineral Groups Element Abundances SILICATES Silica (Si. O 4)4 - Common cations that bond with silica anions All others: 1. 5%

Mineral Groups • • Silicates (most abundant) Non-silicates (~8% of Earth’s crust) – – – Oxides Carbonates Sulfides Sulfates Halides Native elements O 2(CO 3)2 S 2(SO 4)2 Cl-, F-, Br(single elements; e. g. , Au)

Mineral Groups Non-ferromagnesian Silicates (K, Na, Ca, Al) Ferromagnesian Silicates (Fe, Mg) Oxides Carbonates Sulfides/sulfates Native elements

Mineral Groups – Silicates 1. Silicates – Tetrahedron • fundamental building block • 4 oxygen ions surrounding a much smaller silicon ion Silicon-oxygen tetrahedron (Si. O 4)4 -

Mineral Groups – Silicates • Joining Silicate Structures – How tetrahedra may be linked: • independent tetrahedra • single chains • double chains • sheets • 3 -D framework

Mineral Groups – Silicates –

Mineral Groups – Silicates Olivine Group dark silicates (Fe-Mg) ferromagnesian No cleavage

Mineral Groups – Silicates Pyroxene Group Ferromagnesian / dark silicates (Fe-Mg) Augite 2 -directions of cleavage (at nearly 90 degrees)

Mineral Groups – Silicates Amphibole Group Ferromagnesian / dark silicates (Ca, Fe-Mg) Hornblende 2 -directions of cleavage (not at 90 degrees)

Mineral Groups – Silicates Mica Group and Clay Minerals light silicates (K, Al) non-ferromagnesian Muscovite 1 -direction of cleavage

Mineral Groups – Silicates Feldspar Group K-feldspar light silicates (K-Na-Ca, Al) Most common mineral group Orthoclase Plagioclase 2 -directions of cleavage (at 90 degrees) Ca/Na-feldspar

Mineral Groups – Silicates Quartz light silicates (pure Si. O 2) no cleavage (conchoidal fracture) hard, resistant to weathering Quartz

Minerals Mineral Groups 2. Carbonates • Minerals that contain the elements carbon, oxygen, and one or more other metallic elements 3. Oxides • Minerals that contain oxygen and one or more other elements, which are usually metals

Minerals Mineral Groups 4. Sulfates and Sulfides • Minerals that contain the element sulfur 5. Halides • Minerals that contain a halogen ion plus one or more other elements 6. Native elements • Minerals that exist in relatively pure form

Sulfides

Native Copper