Minerals Flashcards
What methods can we use to test minerals to determine what it is?
Hardness
Streak
Lustre
Cleavage
Colour
Relative Density
Other unique features
What is hardness?
The mineral’s ability to resist scratching or abrasion
What do we use to measure hardness?
Moh’s scale of hardness
What levels of hardness are ascertained using
a) fingernail
b) copper coin
c) steel pin
a) 2.5
b) 3.5
c) 6.5
What is streak?
The colour of the mineral in powder form
What can we use to determine streak?
a streak plate
What is colour?
What colour the mineral is
What is lustre?
The way in which a mineral reflects the light
Which minerals are easy to identify by colour?
Olivine - green
Pyrite - gold
Chalcopyrite - bronze/yellow with peacock tarnish
Galena - grey
What types of lustre are there?
Vitreous
Pearly
Silky
Metallic
Give some ‘other’ properties that are unique or rare to some minerals
CRYSTALS:
- quartz = square and pointy
- fluorite = cubic
EFFERVESCENCE:
- calcite = 0.5M HCl
TARNISH
- chalcopyrite - peacock colours
What crystal shape is quartz?
hexagonal prism terminated by a pyramid
What crystal shape is garnet?
football shaped ish, rhomb shaped faces
What crystal shape is calcite?
rhombic shaped
What crystal shape is flourite?
cubic or octahedral crystals
What crystal shape is galena?
Cubic
What crystal shape is gypsum?
fibrous/twinned
What crystal shape is haematite?
kidney shaped masses like aero
What crystal shape is barite?
bladed crystals (flat like a blade), sometimes form cockscomb masses/desert rose
What crystal shape is chiastolite/andalusite?
needle crystals with square cross section, black centre, acicular (needle shaped)
What is cleavage?
The tendency of some minerals to break along lines of weakness
- produces flat shiny faces
- if it has no cleavage, it is hard to break, it will fracture unevenly
What is fracture?
Give an example
How a mineral with no cleavage breaks (unevenly)
e.g. quartz has conchoidal fracture, it breaks with curved faces
What is the difference between hornblende and augite?
HORNBLENDE:
- cleavage planes at 60+120 degrees to each other
- normally hexagonalish
- shiny and splintery looking
AUGITE:
- cleavage planes at 90 degrees to each other
- mediocre cleavage
- normally squareish
- little, well formed crystals
- very dark green (nearly black)
- blocky shape
What is the difference between orthoclase and plagioclase feldspars?
ORTHOCLASE: pink/flesh coloured
PLAGIOCLASE: white, multiple twins are black/white under a microscope
BOTH ARE OPAQUE
What is twinning?
where two or more crystals of the same mineral grow in a symmetrical relationship with each other
- the intergrowth of two or more crystal segments
e.g. reflection/rotation
What is the element composition of the Earth and its percentages?
Oxygen 47%
Silicon 28%
Iron 8.1%
Aluminium 5%
Calcium 3.6%
Sodium 2.8%
Potassium 2.6%
Magnesium 2.1%
Other 0.8%
What is a silicate tetrahedra?
a very strong and stable combination that easily links up together in minerals, sharing oxygens at their corners
- 3 ways to draw
- silicates the most common minerals in the crust and mantle (95% crust, 97% mantle)
e.g. SiO2 = quartz
(Mg/Fe)2SiO4 = olivine
What is a mineral?
inorganic, naturally forming crystalline substances that are the ingredients that make up rocks
What two categories can we divide rocks into
Crystalline
Clastic
What does crystalline mean?
What types of rocks are crystalline?
the grains are interlocking
- they have CRYSTALS
IGNEOUS/METAMORPHIC
What does clastic mean?
What type of rocks are clastic?
the grains are not interlocking
- they have CLASTS
SEDIMENTARY
What does texture mean?
What does it incorporate?
the grains and their relation to each other
- texture
- shape
- size
- relative size (all same/different)
