Introduction to Minerals Flashcards
Define Minerals
A naturally occurring, inorganic, solid, crystalline substance which has a fixed structure and a chemical composition which is either fixed or which may very within certain defined limits
What are mineraloids
- amorphous solid materials without a fixed composition, i.e. they lack a crystal structure
- can be organic
- can be manmade
Minerals are ________ solids.
crystalline
Crystals are…
solids naturally bounded by flat faces meeting at sharp edges
Crystal lattices are…
a crystal shape which reflects the regular arrangement of constituent atoms
What 2 elements make up 75% of the earth’s crust
Oxygen and Silicon
Most common mineral in earth’s crust
Silicate
Minerals are made up of ______
bonded atoms
What are the three main types of atomic bonding
- Ionic
- Covalent
- Metallic
Ions are…
atoms with positive or negative charges due to loss or gain of electrons
Anion
an atom that has gained electrons
- has a negative charge
- has more electrons than protons
Cation
an atom that has lost electrons
- has a positive charge
- has less electrons than protons
Ionic Bond
attraction of oppositely charged ions
Covalent Bond
atoms share electrons
what does ionic radius determine
How ions pack together to form minerals
Coordination number
The number of anions around each cation in a crystal lattice and is controlled by ionic radii
Radius ratio
radius of cation/radius of anion
Coordination number and radius number relationship
coordination number increases with radius ratio
The unit cell
the smallest arrangement of atoms which may be repeated regularly in three dimensions to form a crystal lattice
How minerals grow
1) first a ‘seed’ forms
2) surrounding ions are attracted and attach to the surface
3) Mineral grows outwards from the centre
4) if space permits large well formed crystal will form
Where do minerals grow in the earth
crust and lithosphere
What are the mineral forming environments for igneous
- High temperature (>700degreesC), so melts
- Pressure and water content variable
- Minerals are able to form in free environment
The igneous minerals that form in this environment are…
- moderately hard to hard
- anhydrous and hydrous
- good crystalline shape
What are the mineral forming environments for metamorphic
- moderate to hight temperature (200 - 700 degreesC) so no melting
- low to high pressure
- abundant water in some cases (metasomatism)
- minerals form in a confined environment and their shape is strongl
