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PROPERTIES� OF MINERALS�

Adapted from Mrs. Turano’s Presentation

MMS

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Bellringer

  • What is a mineral?

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  • How are minerals formed?

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I. What is a mineral?

  • Characteristics:

1. Minerals naturally occur

2. Inorganic

3. Solid

4. Has a crystal structure

5. Has a definite chemical composition

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Pyromorphite

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1. Naturally Occurring

  • Naturally Occurring means that the substance must occur in nature, it can not be created or manufactured by people.
  • For example, steel, brass, and bronze are not considered minerals in that they are not found in nature.

Tourmaline Crystal from Brazil

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2. Inorganic

  • Inorganic means that a mineral can not come from something that was once living.
  • Minerals are NOT produced by organic processes, therefore pearls, coral, coal and amber are not considered minerals.

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3. Solid

a. A Solid has a definite volume and shape, held by chemical bonds.

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b. It is the strength of the chemical bonds that determine many of the minerals’ physical and chemical properties.

Halite (salt) from Searles Lake, CA

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4. Crystal structure

a. Crystal structure means the particles line up in a pattern that repeats over and over again.

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b. A crystal has flat sides called faces that meet at sharp edges and corners.

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4. Crystal structure

Top left from http://www.tuspirits.com/images/ArkansasCrystal867.jpg

Top Right http://judie.co.nz/wp-content/uploads/2010/02/quartz_crystal_cluster_black.jpg

Bottom Left http://www.mindat.org/photos/0554307001221343359.jpg

Bottom Right http://t1.gstatic.com/images?q=tbn:ANd9GcSML6stZDnpe1vLvdPfB

3uOjrscEi3qsGmQpQ4LGwERlyB-Iww&t=1&usg=__7mdDC9sp-_A5hsegmp5Tp6eDizY=

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5. Definite chemical composition

  • Definite chemical composition means that a mineral always contains certain elements in definite, or exact, proportions

b. Almost all minerals are compounds: two or more elements are combined so they no longer have their distinct properties.

c. Some elements occur in a pure form in nature and are considered minerals (almost all are metals such as copper, aluminum, silver, and gold)

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Which 2 of the following are not minerals? WHY?

  • Talc Flourite
  • Galena Crude Oil
  • Quartz Pyrite
  • Coal

Bellringer

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Which 2 of the following are not minerals? Why?

  • Talc
  • Flourite
  • Galena
  • Crude Oil- liquid (not solid) and organic (made of plant and animal remains)
  • Quartz
  • Pyrite
  • Coal- Organic (made of plant and animal remains)

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II. Identifying Minerals

  • Each mineral has its own specific properties that can be used to identify it, because each mineral has its own unique makeup.

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  • Minerals are identified by PHYSICAL characteristics

such as...

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Minerals are identified by PHYSICAL characteristics

1. Hardness- Mohs Hardness Scale

2. Color

3. Streak

4. Luster

5. Crystal Systems

6. Cleavage and Fracture

7. Special Properties

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Bellringer

  • What are a few ways that minerals are identified?

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  • What does inorganic mean?

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1. Hardness- Mohs Scale

  • Hardness (how hard a mineral is) is one of the BEST ways of identifying a mineral.
  • Hardness tests are done by scratching one mineral against another. The mineral that is scratched is softer than the other.
  • Mohs Hardness Scale ranks 10 minerals from softest to hardest,
    • 1 Talc is softest
    • 10 Diamond is hardest

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Hardness- Mohs Hardness Scale

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Quartz is harder than glass.

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2. Color

  • Color can be tricky- easily noticed but NOT the best property for identifying.
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  • Color can only be used for a few minerals that have their own specific color

Various colors of CALCITE.

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2. Color – �Shades of Quartz

Clear - Without Impurities

Amethyst

Ionic Iron

Quartz comes in a wide range of colors. It is very easily colored by even trace amounts of impurities.

Smoky Quartz

Raw natural vermarine

Some Pics from Wikipedia

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3. Streak

  • Streak tells the color of a mineral’s powder.
  • Rub the mineral against an unglazed tile - a streak plate.
  • The color of the streak can be different than the mineral

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4. Luster

  • Luster describes how a mineral reflects light from its surface.
  • Metallic = shiny like metal
  • Non-metallic = dull, non-shiny surface

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Pyrite has a metallic luster

Calcite has a non-metallic luster

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5. Crystal Systems

a. Crystals of minerals grow atom by atom to create that mineral’s crystal system.

b. Geologists classify crystal systems into six groups based on the number and angles of the crystal faces

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5. Crystal Systems

Image from http://www.mindat.org/photos/0547579001219485816.jpg

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6. Fracture/Cleavage

  • All minerals fracture or break. Some will break along flat planes, or cleave.
  • Cleavage is a property that describes a mineral that splits evenly along flat surfaces
  • Cleavage is due to how

atoms are arranged in the

crystals of a mineral.

https://courses.lumenlearning.com/geology

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6. Cleavage

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Fracture

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Fracture describes how a mineral looks if it breaks in an irregular way and does not split apart evenly -- Think of bones, bones fracture

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Common Fracture Descriptions

Fracture describes how a mineral breaks into forms or shapes other than flat surfaces.

1. Conchoidal: describes a curved, nearly rounded, smooth fracture that looks like the inside of a shell.

2. Fibrous: fibers.

3. Splintery: stiff, sharp, needle-like pieces.

4. Hackly: rough edges.

5. Uneven or irregular: rough, uneven surfaces.

http://www.kidsloverocks.com/html/mineral_cleavage.html

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7. Special Properties

  • Some minerals have special physical properties that help to identify them:
  • Fluorescence

means that

mineral can

glow under

UV light

(image from Wikipedia)

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Special Properties...

  • Double Refraction produces two images when something is viewed through the mineral

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Special Properties...

  • Magnetic
  • Smell
  • Taste…(Don’t eat my mineral samples!)
  • Fizzing when exposed to acids
  • Radioactivity

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Other Notes...

  • There are about 2500 minerals on Earth
  • The most common 100 are made with 8 elements:
    • Si, O, Al, Fe, Mg, Ca, Na, K
  • Quartz is most common (SiO2)

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Mineral Formation from Molten Rock

Molten Rock- liquid rock containing dissolved pieces of rock, gases and minerals

  • Magma molten rock below Earth’s surface
  • Lava molten rock above Earth’s surface

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Mineral Formation

Magma-

  • Insulated from cool air and water therefore cools slowly
  • Large crystals

Lava-

  • Cools and hardens quickly in air
  • Small crystals

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Minerals...

Pegmatites-

Examples:

  • Silicates
  • Felsic minerals
  • Mafic minerals

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Minerals from Solution

Solution

Evaporation

Crystallization

Precipitation

Stalactite- Hang down

Stalagmites- Rise up

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Minerals form Metamorphism

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Minerals

Ores

  • Metallic minerals
  • Non-metallic minerals

Gemstones

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