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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