eals: chap 2 minerals

is created when part of the creature, like bone is preserved in a substance.

minerals

characteristics of minerals

• natural

• inorganic

• crystalline

• definite chemical composition

• solid

is the external expression of the internally ordered arrangement of atoms.

crystal form

6 major Crystal Forms

1. isometric

2. tetragonal

3. orthorhombic

4. hexagonal

5. monoclinic

6. triclinic

are block shaped with relatively similar and symmetrical faces. The crystal form has three axes all at 90° angles and all the same length.

Axes Length Relationships: A = B = C

isometric

shaped like four-sided pyramids or prisms. The crystal form has three axes that are all perpendicular to one another. Two axis have the same length, and one is different.

Axes Length Relationships: A = B ≠ C

tetragonal

are shaped like a rectangular prism with a rectangular base. The crystal has three axes of different lengths and intersect at 90° angles.

Axes Length Relationships: A ≠ B ≠ C

orthorhombic

have three symmetrical axes that occur in the same plane and are all the same length. The fourth axis may be either longer or shorter, and it intersects the other three axis at 90° angles.

Axes length Relationships: A = B = C ≠ D

hexagonal

are short and stubby with tilted faces. Each crystal has three axes that are unequal. Two of the axes lie in the same plane at right angles to each other, the third axis is inclined.

Axes Length Relationships: A ≠ B ≠ C

monoclinic

s have three axis which are all different lengths and all three axis intersect at angles other than 90°.

Axes Length Relationships: A ≠ B ≠ C

triclinic

7 Major MineralGroups:

1. Silicates

2. Native Element

3. Halides

4. Carbonates

5. Oxides

6. Sulfates

7. Sulfides

are composed of silicon-oxygen tetrahedrons, an arrangement which contains four oxygen atoms surrounding a silicon atom

silicates

are minerals that are composed of a single element

native elements

consist of halogen elements, chlorine (Cl), bromine (Br), fluorine (F), and iodine (I) forming strong ionic bonds with alkali and alkali earth elements sodium (Na), calcium (Ca) and potassium (K)

halides

are anionic groups of carbon and oxygen. these minerals often result from bonds between these complexes and alkali earth and some transitional metals

carbonates

are minerals that include one or more metal cations bonded to oxygen or hydroxyl anions.

oxides

are minerals that include SO4 anionic groups combined with alkali earth and metal cations.

sulfates

are minerals composed of one or more metal cations combined with sulfur.

sulfides

Physical Properties of Minerals

• Hardness

• Color

• Luster

• Streak

• Cleavage

• Fracture

• Specific Gravity

the ability of a mineral to resist abrasion or scratching on its surface.

hardness

refers to how light is reflected from the surface of a mineral.

luster

2 types of luster

• metallic

• non-metallic

are described as shiny, silvery, orhaving a metal-likereflectance

metallic luster

described as resinous, translucent,pearly, waxy, greasy, silky, vitreous/glassy, dull, or earthy

non-metallic luster

is determined by how the crystals absorb and reflect light.

color

refers to the color of a mineral’s powdered form left behind after it is scraped or rubbed across a porcelain streak plate.

streak

refers to the tendency of a mineral to break along planes of weakness in the chemical bonds, or along planes where bond strength is the least.

cleavage

refers to the non-planar breakage of minerals. it may be described as splintery, uneven, or conchoidal or hackly.

fracture

curved concavities resembling shells

conchoidal

rough and completely irregular surfaces, the commonest fracture type

uneven

partially separated splinters or fibres

splintery

Sharp, jagged edges

hackly