minerals - val test term 4 yr 8

minerals must be

• at a solid state under normal conditions

• naturally occuring on earth

• inorganic

• fixed chemical formula with specific elements

• atoms arranged in a specific structure

colour

depends on how light is absorbed, which is determined by chemical composition. however, colour can vary within minerals due to intrusions or variations

chemical composition

what chemicals go into a mineral, as well as the formula of the mineral

crystalline habit

minerals form into shapes at a macro level due to their crystal structure, that shape is the crystalline habit of the mineral

cleavage

the way minerals break

crystal structure

how atoms in the crystal are arranged on a molecular/atomic level, repeating within the mineral

elemental composition

what elements make up a mineral

streak

the colour of the mineral in powder form

hardness

the property of being rigid and resistant to pressure; not easily scratched
determines the minerals use

mohs hardness scale

a measure of a material's relative hardness based on its ability to scratch another material with a known hardness, on a scale of 1-10

lustre

the way light reflects off a minerals surface

transparent

a mineral is transparent if it lets all light through it

translucent

a mineral is translucent if it lets partially some light through it

magnetism

attraction for iron; associated with electric currents as well as magnets; characterized by fields of force

density

how tightly atoms are packed together in the mineral. can make some minerals lighter or heavier

garnet is commonly found in

metamorphic rocks, more rarely igneous

garnet mining sites

tanzania, india, madagascar

garnets magnetism

can vary depending on the variation, as some have more iron or aluminium in them, however overall they are not magnetic.

lustre of garnets

vitreous/glass to resinous

garnet's mohs hardness scale

6.5 - 7.5

garnet's elemental composition

10% silicon, 40% oxygen, 20% trivalent cations, 30% divalent cations

garnet's crystalline habit

can vary, but mostly rhombic dodecahedral, trapezohedral, and hexoctahedral

garnet's crystal structure

octahedral or tetrahedral framework within an isometric system

garnet's chemical composition

formula - X3Y2(SiO4) where x is replaced by divalent cations such as calcium, magnesium or iron, while y is replaced by trivalent cations such as iron, aluminium, and chromium

garnet's colour

can be any colour, but red is most common
this is because of variation and many impurities