Minerals Flashcards
define element
A substance made up of only one type of atom
9 most abundant elements in the Earth’s crust
Oxygen 46.6% sodium 2.8%
silicon 27.7% pottasium 2.59%
aluminium 8.13% magnesium 2.09%
iron 5% other <1.5%
calcium 3.63%
5 requirements for something to be a mineral
1.exists as a solid in normal conditions
2.must be naturally occurring
3.inorganic
4.fixed chemical formular
5.atoms must be arranged in a orderly crystalline structure
mineral examples
Quartz, Mica, Diamond, Talc, Sulfur, Graphite.
Formation of minerals
minerals form from liquid
the liquid is usually molten material
if it cools quickly there are smaller crystals formed
if it cools slowly bigger crystals occur as the haven’t had as much time to form
how do minerals grow
they grow from the center outwards
they have a definite shape
they grow by adding faces
the angle between the faces always stays the same
if they form in a void they will have a well defined shape if the meet another mineral it will form a grain boundary and the shape will look irregular
define a rock
a aggregate of 1 or more minerals
Common crystal habits
Isometric e.g. diamond
Hexagonal e.g. emerald
tetragonal e.g. wulfinite
Trigonal e.g. quartz
Orthorhomnic e.g. topaz
monoclinic e.g. malachite
triclinic e.g. feldspar
what are some characteristics of rock forming minerals?
part 1
Colour- diff minerals have diff colours
streak- residue left by a mineral when dragged across a streak plate
lustre- the ability of a crystal to reflect light metallic, dull, pearly, vitreous, silky
shape- diff mineral have diff shapes due to the arrangements of atoms
what are some characteristics of rock forming minerals?
part 2
cleavage and fracture- some minerals have cleavage planes/ planes of weakness some have more than 1
hardness- diff minerals have diff hardness
density-diff minerals have diff densities
reaction with acid- some minerals react with acid (weak HCl) if so they will fizz or bubble.Carbonate minerals react
Mohs hardness scale
1.talc 1-2 fingernail
2.gypsum
3.calcite 3- 2p coin
4.fluorite 4-5 steel blade
5.apatite
6.feldspar 6-steel blade sometimes
7.quartz 7-10 scratch glass
8.topaz
9.corundum
10.diamond
How to carry out a hardness test
Find a flat surface of unknown mineral
take the reference material and find sharp edge/corner
drag ref material across the unknown mineral
if a scratch is produced unknown is softer than ref, if not it is harder
select the next hardness ref material up or down the scale and repeat test
how to measure mineral density
zero the balance
place sample on balance + record mass
put know volume of water in measuring cylinder
place sample in the water
record new water level reading
dispalcment=volume of sample (1ml=1cm³)
then calculate density using D=M/V
Cation definition
a positively charged ion (lost electron)
Anion
a negatively charge ion (gain electrons)
Silica tetrahedron structure and charge
Silicon and oxygen atoms are attracted to each other because they can share electron
covalent bond- sharing electrons forms covalent bonds
A tetrahedron is a triangular pyramid
A Silica tetrahedron is made up of 1 Silicon atom and 4 oxygen atoms (SiO4‐⁴)
Oxygen in the corners and silicon in the middle each oxygen shared 1 electron with silicon so it has a full outer shell but oxygen has a spare electron causing the Silica tetrahedron to have a 4- charge overall
single tetrahedra
simplest silicate mineral structure is the single tetrahedron
An example of a mineral with this structure is olivine
The tetrahedron are not directly bonded to eachother other elements join or link them together
Silica tetrahedron Chains
Silica tetrahedra can form chains
when each tetrahedron shares 2 of its oxygen atoms
shares 2 electron on 1 oxygen corner
When Silica tetrahedron shares some of its electrons this is called bridging oxygen
Chains still have not achieved a balanced charge
e.g. Pyroxene
Silica tetrahedron double chain
in a double chain some of Silica tetrahedra form 3 bridging oxygen and some form 2 bridging oxygen
when 2 single chains are combined we form a double bond chain structure
e.g hornblend
Silica tetrahedron sheets
sheet structure form when each tetrahedra forms 3 bridging oxygen at 3/4 point
e.g Mica
Minerals with a sheet structure have bonds that form to hold the sheets together but those bonds are usually very weak
These minerals have a good cleavage
Silica tetrahedra framework
form when all 4 O form bridging O/ are shared by adjacent tetrahedra
Minerals with this structure tend to be strong and hard ad they are strongly bonded in every direction
e.g. Quartz
polymerization what it means+ how it relates
A polymer consists of repeating chains of smaller molecules
some smaller chains join to make polymers- polymerization
Silica tetrahedra form polymers through oxygen sharing/bridging
The more polymerization in a lava or Magma the slower the flow
Sedimentary rock definition+ formation
A rock composed of fragments that habe been deposited, compacted and cemented
Most sediments are a result of weathering/erosion
weathering is the breaking up of the rock and erosion is the transportation of fragments
They are transported by wind or water
as energy levels decrease sediments is deposited over millions of years more and more is deposited
burial causes compaction
usually form layers, sometimes contain fossils
igneous rock definition+ formation
A rock that crystallized from a Magma
Composed of interlocking crystals
Crystals do not usually have any preferd
aliment, the crystals have grown in all different directions
2 catagories:
intrusive- are formed from Magma and formed in the crust
extrusive- are formed from lava and cool on the surface
intrusive cool slower so have larger crystals
