What is a Mineral

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What is a Mineral?

• A mineral is a
• Naturally occurring,
• Inorganic,
• Crystalline solid,
• That has a definite chemical composition.

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Some Minerals
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What is a Rock?

• A rock is a
• Naturally formed,
• Consolidated material,
• Composed of grains of one or more minerals.

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Some Rocks
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Mineral Characteristics

• Minerals are classified based on their physical
  properties and chemical properties.

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How Do We Identify Minerals?

• We identify minerals using physical properties
  of
• Color and streak
• Luster
• Hardness
• Cleavage
• Fracture

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Color and Streak

• Color is the first thing that most people notice
  about minerals.
• Color is a useful property but many minerals are
  found in a variety of colors.
• Streak is the pulverized color of a mineral.
• Streak is determined by scraping the sample
  across a porcelain plate.

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Luster

• Luster is the quality and intensity of the light
  that is reflected from the surface of a mineral.
• Luster is described as metallic or non-metallic.
• Non-metallic is more common, most importantly is
  glassy.
• Earthy luster is uncommon but appears silky, or
  pearly.

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Earthy and Metallic Luster
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Hardness

• Hardness is a minerals resistance to being
  scratched, or the scratchability of a mineral.
• In order for a mineral to scratch another it must
  be harder.
• Frederich Mohs made up a scale, called the Mohs
  Scale, to compare hardness.

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Cleavage

• Cleavage is the tendency of a mineral to break
  along one or more smooth, flat, lustrous
  surfaces.
• Cleavage is described as perfect, good, or poor.
• Different minerals have different planes of
  cleavage.
• Examples mica has one perfect plane, halite has
  three perfect planes

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Fracture

• Fracture is the way a mineral breaks other than
  cleaving.
• Fracture is an irregular break pattern
• Fracture can be described as uneven, conchoidal
  (shell-like), splintery, earthy (like clay)

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Formation of Minerals

• All minerals are crystalline, ,made of atoms
  arranged in a pattern.
• Crystals are minerals with geometric shapes and
  smooth flat surfaces called faces.
• Each kind of mineral has its own crystal shape
  and will develop into this form if it has room to
  grow w/o restrictions.

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Various Crystals
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6 Basic Crystal Systems

• Cubic
• Hexagonal
• Orthorhombic
• Monoclinic
• Tetragonal
• Triclinic

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Chemical Composition

• All minerals are made of elements and some
  minerals can be identified by their special
  chemical composition.
• Some minerals are made up of only one element
  (such as gold, copper, sulfur).
• Most minerals are made of compounds, two or more
  elements chemically combined.

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Chemical Composition - Silicates

• Silicates are the most common minerals and are
  combinations of silicon and oxygen with other
  elements.
• Examples are quartz, feldspar, mica and
  hornblende.

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Silicates
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Chemical Composition - Carbonates

• Carbonates are minerals which are compounds of 1
  carbon atom and 3 oxygen atoms.
• Examples are calcite and dolomite.

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Carbonates
Calcite
Dolomite
Calcite Color Varieties
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Chemical Composition Oxides and Sulfides

• In an oxide, the mineral iron combines with
  oxygen.
• Example is magnetite
• In a sulfide, the mineral iron combines with
  sulfur.
• Example is pyrite (fools gold)

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Oxides and Sulfides
Magnetite (Lodestone) and Pyrite (Fools Gold)
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Structure of Minerals

• Structure refers to the arrangement of the atoms
  in a mineral.
• Silicon and oxygen, the most common elements in
  the Earths crust, combine chemically to form a
  structural unit in the shape of a tetrahedron (a
  four-sided solid triangle)

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