Minerals Earth Science

What is a Mineral?

In Geology… A mineral is a naturally occurring, inorganic solid that has a crystal structure and a definite chemical composition. Some examples…

Naturally Occurring… Seen in nature. Not man made.

Inorganic… Cannot form from material that was once living Cannot form from material that was once living Organic = life! Organic = life!

Crystal Structure… Mineral particles line up in a pattern that repeats itself over and over again.

Definite Chemical Composition Definite = always the same Minerals always contain the same elements in the same ratios. SiO 2 KAlSi 3 O 8

Solid… Definite volume and shape

How do Minerals form? Crystallization of melted material (aka magma/lava) Minerals form as magma cools Crystallization of materials dissolved in water When hot water cools or evaporates, minerals crystallize

Where do we find Minerals? Most of Earth’s crust is made up of common minerals (like quartz) Less common minerals are not evenly distributed around the planet Many valuable minerals are found in or near areas of volcanic activity or mountain building.

Where can you find diamonds? Where can you find oil?

Why do we care? All rocks are made of at least one mineral! How can we differentiate minerals and rocks?? Many minerals are important to our daily lives Gemstone Metals (Silver, copper) In foods, medicines, fertilizers, building materials

Is it formed in nature? Is it non-living material? Does it have a chemical composition? Does it have a crystalline structure? Is it solid?

Wood

Gold

Fossil

Topaz

Bones

Granite

Quartz

Pearls

Talc

Icebergs

Diamond

Coal

Glass

Minerals 2 - Gold 4 - Topaz 6 - Quartz 9 - Talc 10 - Iceberg* 11 - Diamonds Non-Minerals 1 - Wood - once living 3 - Fossils – once living 5 - Bone - living material 7 - Granite - intrusive igneous rock 8 - Pearls – made by oysters 12 - Coal - Sedimentary rock 13 - Glass-Human made * According to IMA – ice is listed as a mineralIMA

MINERALS 1. Naturally occurring 2. Inorganic 3. Solid 4. Crystal structure (due to internal arrangement of atoms) 5. Definite chemical composition

General Facts about Minerals  Over 5,000 have been identified  A few are “native elements” -- made of only one element, such as sulfur, gold. copper, and graphite (carbon)  Most are compounds, especially the silicate group (Si, O). Earth’s crust is 90% silicate rocks!  Other important groups are oxides, carbonates, and sulfides.

Less than a dozen are common in most rocks  Quartz  Feldspar (group)  Muscovite (white mica)  Biotite (black mica)  Calcite  Pyroxene  Olivine  Amphibole (group )  Magnetite, limonite, and other iron oxides  Pyrite We will identify many of these in our LAB activity : )

Silicates  Silicon and oxygen are two of the most abundant elements on earth  Silicates are the most plentiful minerals on earth  They are built around covalent bonds (Chemistry!) of silicon and oxygen Symbols  Silicon = Si  Oxygen = O

Silicates can build in a variety of ways OSi O O O O O OO OO O O O O O O O In flat sheets like mica

Or in crystals 0 Si Si Or in crystals like quartz

Minerals are identified by their key characteristics  Hardness  Crystal structure  Luster  Color  Streak  Cleavage/fracture  Density Special Properties  reaction to acid  fluorescence  salty taste  magnetism  odor

Mineral Hardness  Ability to scratch another mineral  Mohs Hardness Scale from 1 (talc) to 10 (diamond)  Quartz (most common mineral) is 7

Color  results from ability to absorb some wavelengths and reflect others  some minerals have characteristics colors

Streak  Color of the powder when rubbed on a “streak plate” (unglazed porcelain)  May be same as hand- specimen or different  Some paint is based on powdered minerals (streaks).

Luster  Describes how light reflects off the surface  Main categories are “metallic” and “non- metallic”  Non-metallic includes “dull,” glassy,” waxy,” “pearly”

Density (Specific Gravity)  All minerals have density (mass / volume), but some are very dense  Examples include galena, magnetite, and gold  Specific Gravity is the density of the mineral compared with density of water

Crystal Shape (Form)  External structure due to internal arrangement of the atoms  Six basic groups of shapes, with about three dozen variations

Mineral cleavage/fracture  A mineral that splits easily along flat surfaces when struck hard--this is called mineral cleavage  Fracture- Describes how a mineral looks when it breaks apart in an irregular way.  A few minerals have both cleavage and fracture

Special Characteristics  Many minerals have some special characteristic that helps us identify that mineral.

Special Characteristics-- Fluorescence  Some minerals will glow when placed under short-wave or long-wave ultraviolet rays  Franklin and Ogdensburg NJ are famous for their fluorescent minerals Fluorescent Minerals

Special Characteristic-- Salty Taste  DO NOT TASTE the MINERALS!  Halite -it will taste salty, just take my word for it.

Special Characteristics-- Magnetism  Many iron minerals will produce an invisible magnetic force field  “Lodestone” was used by Vikings more than 1,000 years ago as compasses

Special Properties- reacts to acid Calcite will bubble up when acid is poured on it.

Common uses include:  Aluminum--packaging, transport, building  Beryllium--gemstones, fluorescent lights  Copper--electric cables, wires, switches  Feldspar--glass and ceramics  Iron--buildings, automobiles, magnets  Calcite--toothpaste, construction