Minerals

1
Minerals

• Minerals are naturally occurring solids
• that are usually inorganic,
• have an ordered, crystalline structure,
• and vary only slightly in their chemical
  composition.
• There are over 4,000 different minerals found on
  the earth, with more discovered each year.
• Only a few dozen of these minerals make up the
  vast majority of the rocks exposed on the Earths
  surface.

http//www.home4schoolgear.com/roandmikit.html
2
What makes minerals different?

• What makes one mineral different from another is
  its chemical make up. Scientist can identify
  one mineral from another using chemical tests.
  For example Quartz always has one atom of silicon
  for every two atoms of oxygen. For us, we need
  to use other ways to identify minerals.

3
The chemical content of most minerals only varies
slightly within the sample. However, it only
takes slight variations to produce significant
color changes. The following are all variations
of the mineral quartz.
http//www.lemonquartz.com/lemon-quartz-gems.php
Image Credit Geological Survey of Canada
photograph
http//www.faceters.com/rough/quartz/index.shtml
Photo Coll. G. Rüdlinger,SVSMF
http//dundee.rokpa.org/shop/index.php?cPath35os
Csidc7a5aa04841b66998914c57205c28413
4
The atomic structure determines most of the
physical properties of minerals. To correctly
identify a mineral you must rely on most or all
of the following properties.

• Physical Properties of Minerals
• Luster
• Density
• Crystal faces
• Hardness
• Cleavage
• Streak
• Color

http//www.johnbetts-fineminerals.com/jhbnyc/diamd
iag.htm
http//academic.brooklyn.cuny.edu/geology/grocha/m
ineral/cleavage.html
5
Color

• Color is easily observed, but color alone
  provides too little information to make an
  identification. As shown before, the same
  mineral can have several different colors, and
  several different minerals can have the same
  color. Below are three minerals that are all
  gold in color, but only one is actually gold.

http//www.california-gold-rush-miner.us/images/py
rite.jpg
http//skywalker.cochise.edu/wellerr/mineral/chalc
opyrite/6chalcopyrite98.jpg
http//www.minerals.net/mineral/elements/gold/gold
1.jpg
6
Streak

• A streak test is one way to help identify a
  mineral. A streak test is when you rub the
  mineral on a white, unglazed piece of porcelain
  tile. What is left behind is the color of the
  minerals powder. Unlike color, the streak of a
  mineral does not vary. Sometimes the streak of a
  mineral is very different than its color.

Metallic hematite
Magnetite
http//gwydir.demon.co.uk/jo/minerals/hematite.htm
http//www.cs.cmu.edu/adg/images/minerals/o/magne
tite1.jpg
http//meteorites.wustl.edu/id/streak.htm
7
Luster

• Luster is how a mineral reflects light. It is
  one property used to help identify minerals. The
  main ways to classify luster are metallic
  glassy (vitreous) waxy, greasy or pearly
  sub-metallic or dull silky earthy (resinous).

http//www.mineralogicalassociation.ca/young/image
s_page/luster.jpg
8
Density

• Density is the comparison of somethings mass to
  its volume. Finding a minerals density may help
  you determine what it is. Since rocks dont come
  in convenient shapes, the easiest way to find a
  minerals volume is to put it in water. Then
  find its mass using a scale. Finally, divide the
  mass by the volume.
• Density mass/volume

9
Hardness

• One of the best ways to determine a minerals
  identity is to test its hardness. In1812,
  Friedrich Mohs invented a hardness scale for
  minerals. It ranks minerals on a scale from 1-10
  based on ten different minerals. You determine
  the hardness number by scratching the mineral
  with different items.

http//www.infowest.com/life/mohs.gif
10
Crystal system

• All minerals have a crystal structure. Geologist
  divide minerals into 6 different groups based on
  the number and angle of the crystals faces.

http//www.geocities.com/asdfasdf23135/crystalsyst
em2.GIF
11
Fracture and Cleavage

• How a mineral breaks apart is one way you can
  tell them apart. If a mineral breaks easily
  along a flat line, it is said to have cleavage.
  If the mineral does not break apart easily or
  smoothly, it is said to have fracture. Fracture
  has several different classifications. Some are
  shell-shaped, hackly, and earthy.

http//academic.brooklyn.cuny.edu/geology/grocha/m
ineral/cleavage.html