Minerals

Natural Solid Inorganic Definite chemical

composition Crystal structure due

to internal arrangement of atoms

http://www.minerals.net/gemstone/index.htm

http://www.mii.org/www.mii.org

General Facts about Minerals

Between 2 - 3,000 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).

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

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 http://www.mii.org/commonminerals.php

Minerals are identified by their key characteristics hardness crystal shape (form) luster color streak

cleavage/fracture density (specific

gravity) special properties --

reaction to acid --fluorescence --salty taste --magnetism

1. Mineral Hardness

Ability to scratch another mineral

Mohs scale from 1 (talc) to 10 (diamond)

Quartz (most common mineral and most dust particles) is 7

http://mineral.galleries.com/minerals/elements/diamond/diamond.htm

2. Crystal Shape (Form)

External structure due to internal arrangement of the atoms

Six basic groups of shapes, with about three dozen variations

http://www.minerals.net/mineral/carbonat/aragonit/aragoni1.htm

3. Luster Describes how light

reflects off the surface Main categories are

“metallic” and “non-metallic”

Non-metallic includes “dull,” glassy,” waxy,” “pearly,” and others http://www.minerals.net/mineral/sulfides/pyrite/pyrite2.htm

http://www.minerals.net/mineral/sulfides/pyrite/pyrite2.htm

4. Color results from ability to

absorb some wavelengths and reflect others

some minerals have characteristics colors

others vary due to chemical differences or impurities (atoms mixed inside the main elements)

http://www.minerals.net/mineral/carbonat/calcite/images/4assortd.htm

5. 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).

http://www.minerals.net/mineral/oxides/hematite/hematit6.htm

6. Mineral cleavage/fracture

Some minerals split along flat surfaces when struck hard--this is called mineral cleavage

Other minerals break unevenly along rough or curved surfaces--this is called fracture

A few minerals have both cleavage and fracture

7. 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

http://www.minerals.net/mineral/elements/gold/gold1.htm

Special Characteristics--1. the “Acid Test”

Carbonates react with dilute HCl and other acids by fizzing or bubbling (releasing CO2 gas)

Special Characteristics-- 2. 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

http://www.sterlinghill.org/Tour%20information.htm

Special Characteristics--3. Salty Taste DO NOT TASTE MOST

MINERALS! Halite is the exception--

it will taste salty

http://mineral.galleries.com/scripts/item.exe?LIST+Minerals+Halides+Halite

Special Characteristics--4. Magnetism

Many iron minerals will produce an invisible magnetic force field

“Lodestone” was used by Vikings more than 1,000 years ago as compasses

http://www.minerals.net/mineral/oxides/magnetit/magneti4.htm

Mineral Identification Key I. Mineral has a colored streak

A. Mineral has a black or grayish streak. B. Mineral leaves a brown or reddish-brown streak. C. Mineral leaves either a blue or a green streak.

II. Mineral does not leave a colored mark on streak plate, but leaves a white streak or scratches the streak plate. A. Mineral will scratch glass B. Mineral will not scratch glass but will scratch a penny. C. Mineral will not scratch a penny, and cannot be

scratched by your fingernail. D. Mineral can be scratched by your fingernail.

Mineral Identification Key

I. Mineral has a colored streak.A. Mineral has a black or gray streak.

1. Has a metallic gold appearance. It leaves a black Streak.= Pyrite

2.Leaves a “lead gray”

streak, and has a bright

silver metallic luster.

It’s heavy.= Galena

I. A. Mineral has a black or grayish streak. 3. Will write on paper

(easily), and feels greasy. = Graphite

4. Is “magnetic” = Magnetite

I. B. Mineral leaves a brown or reddish-brown streak. 1. Has brown circles

on it’s surface. = Bauxite

2. Has a bumpy surface. = Hematite

I. C. Mineral leaves either a blue or a green streak. 1. Green streak. =

Malachite (Often appears with

Azurite.)

2. Blue streak.=Azurite (Often appears with

Malachite)

Mineral Identification Key

II. No colored mark on the streak plate, but leaves a white streak or

scratches streak plate.

1. Clear or translucent. Has a hardness of 7.= Quartz If Pink = Rose Quartz. If Dark = Smoky Quartz.

II. A. Will scratch glass. Hardness 6-10

II. A. Mineral will scratch glassHardness: 6-106-10 5. Is orange and white in color. It has a hardness of 6. Distinct 90 E cleavage. = Feldspar

3. Mineral is reddish-purple in color and has a hardness of 9. = Corondum

II. B. Mineral will not scratch glass, but will scratch a penny. Hardness: 4-54-5 1. Mineral is light

green in color and has a hardness of 5. = Apatite

5. Translucent and writing appears double when looking through it. = Calcite

II. B. Mineral will not scratch glass, but will scratch a penny.

4. Transparent to translucent. Mineral varies in color. It is often purple. Often shows good cleavage. = Fluorite

II. C. Mineral will not scratch a penny, and cannot be scratched by your fingernail. Hardness: 2-32-31. Mineral has cubic

cleavage and tastes salty. = Halite

2.Is in think flat sheets and peels off in layers. In Mica Family.-Dark Mica=Biotite-Light Mica=Muscovite

II. D. Mineral can be scratched by your fingernail. Hardness: 1-1-22

1. Mineral feels soapy and has a hardness of one. = Talc

2. Transparent or translucent and has good cleavage. Mineral has silky luster and hardness of two. = Gypsum

Useful Web Sites

www.mii.org www.mineral.galleries.com/minerals www.mineral.net www.usgs.gov http://geology.about.com/library/bl/images/

blmineralindex.htm