Properties of Minerals Chapter 2.3 Mrs. Schwartz

Properties of Minerals Definition of a Mineral: naturally occurring inorganic solid characteristic crystalline structure definite chemical composition

How can we identify minerals? Physical properties: Color Cleavage Streak Fracture Luster Density Hardness Special Properties (distinctive) Crystal form

Color LEAST USEFUL PROPERTY, CHANGE IN THE CHEMICAL FORMULA WILL VARY THE COLOR OF THE MINERAL. (QUARTZ) SiO2

Streak the color of a mineral in its powdered form. Obtained by scratching a mineral on a piece of unglazed porcelain.

Luster THE WAY A MINERAL SHINES IN REFLECTED LIGHT. Different kinds of luster: Metallic Non-metallic Waxy Earthy

Luster - Metallic METALLIC- LOOKS LIKE METAL IN THE WAY THE MINERAL REFLECTS LIGHT (GALENA OR PYRITE)

Luster- Non-metallic NON-METALLIC- DOES NOT LOOK LIKE POLISHED METAL, SO OTHER TERMS ARE USED

Other lusters  WAXY- DULL SHINE LIKE CANDLE WAX (SULFUR, OLIVINE)  EARTHY- NO SHINE AT ALL (BAUXITE)

Crystal Form Crystal Form (or shape): external expression of a mineral’s internal atomic structure planar surfaces are called crystal faces angles between crystal faces are constant for any particular mineral

Hardness How easy it is to scratch a mineral Mohs Scale of Hardness relative scale consists of 10 minerals, ranked 1 (softest) to 10 (hardest)

Mohs Scale of Hardness Hardest (10) – Diamond Softest (1) – Talc Common objects: - Fingernail (2.5) - Copper penny (3.5) - Wire nail (4.5) - Glass (5.5) - Streak plate (6.5)

Cleavage the tendency of a mineral to cleave, or break, along flat, even surfaces.

Fracture Minerals that do not show cleavage when broken are said to fracture. Fracture—the uneven breakage of a mineral

Defined as the mass divided by the volume. Density Defined as the mass divided by the volume.

Special Properties MAGNETIC – THE ABILITY TO ATTRACT A MAGNET (MAGNETITE) EFFERVESCENCE – ADDING HCL TO A MINERAL CAUSES IT TO FIZZ TASTE – HALITE

Special Properties ODOR – SOMETIMES THE POWDER OF A MINERAL HAS A CERTAIN ODOR (SULFUR SMELLS LIKE ROTTEN EGGS) DOUBLE REFRACTION – SPLITS LIGHT RAYS (CALCITE)

Special Properties FLUORESCENCE – THE ABILITY TO GLOW UNDER ULTRA VIOLET LIGHT (SPHALERITE) SPECIFIC GRAVITY (DENSITY) – SOME MINERALS HAVE ATOMS VERY TIGHTLY PACKED, AND FEEL HEAVIER BECAUSE THEY ARE MORE DENSE (GALENA)