Rock and Mineral Review

Cleavage Cleavage and Fracture are minerals properties that describe the way a mineral breaks when stressed. Cleavage describes the way a mineral breaks along its plane of weakness. These planes of weakness can be described as where the atomic bonding between atoms in the crystal structure is weak at those points causing the mineral break when stressed much like a stack of papers when drop will spread off in individual sheets.

Fracture Fracture is a mineral property where the atomic bonding between atoms in the crystal structure is perfect with no weakness. When these minerals are stressed they shatter making no two pieces truly the same.

Moh’s Hardness Scale

Galena Cleavage = Cubic Solubility = None Hardness = 2 – 2.5 Color = Silver Gray/Black Magnetism= None Streak = Gray Luster = Metallic Other Characteristics = Has same chemical formula as Pyrite, Heavy for its size (Dense), Ore of Lead, Brittle.

Magnetite Cleavage = None Solubility = None Hardness = Color = Black to Gray Magnetism= YES! Streak = Black Luster = nonmetallic Other Characteristics = Fe 3 O 4, Ore of Iron.

Quartz Cleavage = None Solubility = HCL Hardness = 7 Color = Colorless/White Magnetism= None Streak = White Luster = Vitreous Other Characteristics = Melted to help clocks keep time

Sulfur Cleavage = None Solubility = None Hardness = 2 Color = Yellow Magnetism= None Streak = Yellow Luster = Dull Other Characteristics = Smells like rotten eggs, Melts easily.

Graphite Cleavage = Perfect basal Solubility = None Hardness = 1 – 2 Color = Gray to Black Magnetism= None Streak = Gray to Black Luster = Sub metallic Other Characteristics = Used in pencils (Not lead), Feels greasy.

Feldspar Cleavage = 2 directions Fracture = Uneven Solubility = None Hardness = 6 Color = Pink/White Magnetism= None Streak = White Luster = Pearly Other Characteristics = The pink hue is granite.

Talc Cleavage = One Direction Fracture = Uneven Solubility = None Hardness = 1 Color = White to Green Magnetism= None Streak = White Luster = Pearly/Greasy Other Characteristics = Feels soapy, Used to make talcum powder, easy to sculpt.

Pyrite Cleavage = None Solubility = None Hardness = 6 – 6.5 Color = Brassy Yellow Magnetism= None Streak = Greenish Black Luster = Metallic Other Characteristics = AKA Fools Gold, Ore of Sulfur.

Gypsum Cleavage = One Direction Solubility = None Hardness = 2 Color = White to Colorless Magnetism= None Streak = White Luster = Vitreous to Pearly Other Characteristics = Used to make drywall.

Hematite Cleavage = None Solubility = None Hardness = 5 – 6 Color = Steel to Silver Gray Magnetism= None Streak = Blood Red to Brown Red Luster = Sub metallic Other Characteristics = Ore of Iron, Used to make Steel.

Calcite Cleavage = 3 Directions Solubility = Bubbles CO 2 Hardness = 3 Color = Variable Colorless to White Magnetism= None Streak = White Luster = Vitreous Other Characteristics = Used for making cement.

Granite Fracture/Cleavage = Irregular Solubility = None Hardness = 5 – 7 Color = Varies Magnetism= None Streak = Colorless to White* Luster = Dull Other Characteristics = Intrusive Igneous Rock.

Mica Cleavage = One Plane Solubility = None Hardness = 2 – 3 Color = White, Gray, Silver white, Brownish white, Greenish white Magnetism= None Streak = Gray Luster = Vitreous Other Characteristics = Electrical insulator.

Corundum Cleavage = None Solubility = None Hardness = 9 Color = Variable Magnetism= None Streak = None - White Luster = Vitreous Other Characteristics = Scratch anything, but diamonds, Rubys, Blue equals Sapphire, Insoluble.

Limestone Cleavage = One Solubility = Yes Hardness = 3 Color = Light Magnetism= None Streak = None Luster = Dull Other Characteristics = “Chemical” Sedimentary.

Marble Fracture Solubility = Yes Hardness = 3 Color = Light Magnetism= None Streak = None Luster = Pearly Other Characteristics = Metamorphic, Parent rock is Limestone or Dolostone