Terms/definitionsof mineral properties Flashcards
(21 cards)
Rock
naturally occurring multigranular aggregate of one or more minerals or mineralloids `
Mineral
naturally occurring inorganic substance with a definite chemical composition and regular internal structure
Mineralloid
A mineral-like substance that does not have a definite chemical composition and is not crystalline
Crystalline
orderly internal structure made up of regularly repeating arrangement of atom, ions or molecules in 3-dimensions
Crystal
A crystalline material having a regular geometric exterior form bounded by crystal faces
Cleavage
the way a mineral breaks along planes of weakness within the crystal structure
Fracture
the way a mineral breaks when it does not break along planes
Conchoidal fracture
break with smooth, curved surfaces like the interior of a shell
Hardness
the resistance that a surface of a mineral offers to scratching
Specific gravity
the ratio of the weight of any volume of a mineral to the weight of the same volume of water
Diaphaneity
the ability of a mineral to transmit light (opaque, translucent, transparent)
Lustre
the appearance of a mineral in reflected light (metallic, non-metallic, sub-metallic)
Streak
the colour of a powdered mineral
Isotropic
they don’t alter the vibration direction of light and are always extinct in XPL
Anisotropic
have crystal shapes that are different in different directions
Birefringence (interference colours)
the differences in velocity of the two light waves after they’ve passed though a mineral
Pleochromism
shows colour changes with rotations under PPL
What is plane polarised light?
Light which is vibrating in one direction.
What is cross polarised light?
?
Observations in PPL
crystal shape, cleavage, relief, colour/pleochromism, alteration
Observations in XPL
twinning, extinction, birefringence
