Minerals •***A mineral is a naturally occurring, inorganic, solid with a crystalline structure and a consistent chemical composition***.
Dec 28, 2015
Minerals•***A mineral is a naturally occurring, inorganic, solid with a crystalline structure and a consistent
chemical composition***.
Biotite
The 5 Characteristics of a Mineral•Naturally occurring - can’t be man made (no
synthetics such as cubic zirconium)
•Inorganic - not made from living organisms
•Solid - No molten rock
5 Characteristics Continued…
•Crystal Structure - elements arrange in a regular and predictable pattern.
•Chemical composition - minor variations allowed
3-D Structure of a diamond
Fundamental Atomic Theory
• Elements cannot be broken down by chemical processes.
• Atoms are the basic component of an element.
• Atoms are composed of a nucleus containing protons and neutrons, with an electron cloud surrounding.
Fundamental Atomic Theory cont...
• Ions: Atoms that have lost or gained an electron and are now charged.
• Cation: Lost an electron, positive (+) charge.• Anion: Gained an electron, negative (-) charge.• Minerals form by combinations of atoms and ions
held together by bonds.
Halite - rock salt
Mineral Identification• Physical Properties: Run tests on the
physical characteristics of the sample.
• Crystal Structure: Shape of the sample.
• Chemical Properties: Reaction to acid, taste, or smell.
$40000.00 Diamond Studded IPod Shuffle.
Physical Properties
• Luster: How the mineral reflects light.
• Is it Metallic (M), or Nonmetallic (NM)?
Physical Properties cont.
• Hardness: Resistance to abrasion.
• Moh’s Hardness Scale• 1 - softest mineral (talc)• 10 - hardest mineral (diamond)• Fingernail - 2.5• Penny - 3.5• Glass - 5.5• Steel Nail - 5.5• Streak plate - 6.5
Breakage• Does the mineral break along flat surfaces?
No - uneven breakage, Fracture (F)
(ex. Quartz)
Yes - mineral splits along parallel planes, Cleavage ( C )
(ex. Halite)
Phys. Properties Cont.• Streak: Color in powdered form.
– Scrape the sample across the streak plate, what color is left behind?
• Specific Gravity (density): Weight of the mineral compared to an equal volume of water.
• Color: LEAST RELIABLE physical property.
Crystal Shape• The arrangement of ions in the atomic
structure determines the crystal shape.
Isometric
Ex. Pyrite
Hexagonal
Ex. Corundum
Trigonal
Ex. Hematite
Tetragonal
Ex. Zircon
Rock Forming Minerals
• Silicates are the largest group of minerals.
• Make up 95% of the Earth’s crust.
• Contain silicon and oxygen.• Silicon - Oxygen tetrahedron,
SiO4
– Each Si is surrounded by 4 Oxygen
– Strong bonds, high hardness.
Important silicate minerals
• Feldspars: 50% of Earth’s crust• Quartz: Abundant in Continental crust• Pyroxenes and Amphiboles• Micas• Olivine: Rare in Continental crust