Geosphere- Minerals Flashcards
Which 4 elements make up 93% of the geosphere?
How do we know this?
Iron
Oxygen
Silicon
Magnesium
It’s impossible to do a chemical analysis of the entire planet, so we use meteorites to determine this composition
The inner 4 planets (list below) and Earth’s moon are similar in size/ structure.
Planets:
-
-
-
-
Structure:
-
-
-
Mercury
Venus
Earth
Mars
- metallic core (molten and solid iron)
- rocky mantle
- thin rocky crust (very variable)
the rocky mantle of the 4 inner planets is composed of mainly which 4 elements?
- Si
- O
- Mg
- Fe
The Earths crust is mostly made up of which 3 elements?
- oxygen
- silicon
- aluminum
Elements in the crust and mantle are organized in minerals. What 5 things define a mineral?
- naturally occuring
- inorganic (don’t contain C)
- soilds
- fixed chemical composition or limited range of composition
- regular internal repeating crystalline structure
About ___ discrete minerals are known, but only ~___ are common on the crust
4000
12
T/F
by the scientific definition of a mineral, ice is a mineral and coal is not
true!
however, in other realms like law, it’s the other way around
rocks=
naturally occurring mixtures of minerals
-
- organic matter
- volcanic glass
The following minerals can be found in a typical rock like granite. What color is each mineral typically?
1. Feldspar
2. Quartz
3. Mica
feldspar= pink and white
Quartz= grey
mica= black
What 3 types of bonding occur in solids?
1
2
3
which is the strongest?
- Ionic bonds
- Metallic bonds
- covalent bonds (strongest)
describe an ionic bond and give an example
an e- in the outer orbital donates to an element missing an e-
= becomes pos and neg charged bonds, which makes them attracted to each other (holds the structure together)
eg. NaCl (Na is + and Cl is -)
describe a metallic bond in a solid
- less common
delocalized e- move around the structure, in between the metal ions (they’re not it orbitals, they just “float” between the ions)
describe covalent bonding and give an example
e- are not donated, but they’re SHARED
- common with carbon
- strongest type of bond
- diamond is covalently bonded
Why don’t we use the chemical formula for minerals? Give an example
Because of polymorphs!
- when minerals have the same formula but different crystal structures (many forms)
eg. diamond and graphite
why do diamonds exists at Earth’s surface if they require such high pressure to form?
b/c they’re transported up to the surface so quickly that they don’t have time to revert to graphite (stable form at surface conditions)
___ is a characteristic of minerals that is not usually diagnostic so it’s not used to identify minerals
color
The following are a few ways to identify minerals. Describe each
- lustre=
- streak=
- external crystal form
(eg)
- lustre= appearance of reflected light (metallic or non-metallic)
- streak= color of powdered mineral on a porcelain plate
- external crystal form= reflects the internal ordering of atoms
eg. quartz has 6 sides b/c the chemical elements that make it up are arranged in a 6-sided ring
The following are a few ways to identify minerals. Describe each
-Cleavage=
- Hardness
what’s used to measure this?
-Density
eg
-Magnetic Properties
eg
- Reaction with acid
eg
-Cleavage=natural parting along planes of internal low bond strength- reflects weakness in crystal
- Hardness= relative resistance to scratching
Use Mohs relative scale of hardness
-Density= can usually tell density by how heavy it is
eg Galena is very dense and heavy
-Magnetic Properties
eg magnetite is magnetic
- Reaction with acid
eg. calcite reacts with acid
which group of minerals is the most common on earth?
silicate group
____ is the “building block” for most minerals on earth
- it has a ___ shape with an overall charge of __ (meaning it wants to bond with __)
SiO4 4-
tetrahedron
4-
positives (forms good bonds with oxygen)
The following Minerals all belong to the ___ group:
- quartz
- feldspar
- clay minerals, ____
- ferromagnesian (FeMg) minerals
(inc ___ and ___)
Silicate
mica
olivine
pyroxene
How are subgroups of silicate minerals characterized?
by how the individual silica tetrahedrons are linked together
- chains
- sheets
- framework (3D)
____ is an isolated silica tetrahedron
- SiO4 is ionically bonded to ___ and/ or ____
Olivine
iron and/or magnesium
could be entirely Mg, entirely Fe, or a bit of both (Fe and Mg are the same size w the same charge)
Describe the structure of chain silicates
give an example of a chain silicate
tetrahedrons share a corner oxygen –> creates a chain
eg. pyroxene (ferromagnesian)
Describe the structure of sheet silicates
give an example of one
sheets= chains attached to each other
eg. mica group- muscovite, biotite
Describe the structure of framework silicates
give an example
sheets are joined in a 3D shape
- framework of SiO4 tetrahedra w some Al instead of Si
- all O atoms are shared b/w tetrahedra in 3D
eg. feldspar group
Both feldspar and Quartz have a framework silicate structure, but how do they differ?
Feldspar-
some Al replaces Si in the framework of SiO4 tetrahedra
Quartz-
there is no substitution of other elements (it’s just a framework of SiO4 tetrahedra)
The following are _______ minerals:
- carbonates
- halides
- sulfates
- oxides (___ and ___)
- native elements like ___ and ___
non-silicate mineral group
hematite and magnetite
gold and diamond
Halides, such as ___(NaCl) form where?
halite
in places where seawater (in warm/ arid enviros) undergoes rapid evaporation (~90% of water evaporated = NaCl will precipitate)
