Minerals Flashcards
What is a mineral?
An element or chemical compound that is crystalline and that has formed as a result of geologic processes.
Minerals must:
Have a crystalline structure (an ordered atomic arrangement).
Be inorganic / naturally occurring
What are glasses?
Solids lacking internal atomic order. (Non-crystalline)
Obsidian
a hard, dark, glasslike volcanic rock formed by the rapid solidification of lava.
How does glass break?
Breaks with a conchoidal fracture, which is a curved breakage that resembles the concentric ripples of a mussel shell.
What are the crystals of gypsum?
They are the largest mineral crystals known and grew by
precipitation from the hot water that previously filled the cave.
Why do minerals fracture?
Minerals that have no lattice planes of weakness—
bonds equally strong in all directions—fracture instead of cleave.
What does “Stilbite” mean?
Greek… “TO SHINE”… refers to a mineral’s luster
What is Malachite?
A copper mineral.
What is Bismuth?
A synthetic mineral, created by humans.
Biogenic minerals
Formed by living organisms
What determines a mineral’s properties?
- The nature of bonding
2. The geometry of the atomic packing
Mineral Halite =
Salt
What are the two polymorphs of carbon?
Diamond (hardest) and Graphite (softest)
What affects mineral growth?
Space; room to grow.
Physical properties to describe a mineral…
- color
- streak
- hardness
- luster
- specific gravity
- crystal habit
- cleavage
What is streak?
a property whereby a mineral leaves a crushed powder on an unglazed porcelain plate. (requires a hardness of less that 6 or so)
What is luster?
a property that refers to the way that a mineral surface scatters light.
What are the two subdivisions of luster?
metallic and nonmetallic (which has many subdivisions).
What is hardness? and what is it linked to?
the scratching resistance of a mineral, which is directly linked to atomic-bond strength
What is used to measure the hardness of a mineral?
The Mohs scale (Scaled from 1-10)
The tendency for a mineral to break along lattice planes with weaker atomic bonds.
Cleavage
How can one distinguish the difference between cleavage and crystal faces?
Cleavage is throughgoing; faces are on external crystal surfaces only.
Examples of cleavage?
- Muscovite (One direction)
- Potassium Feldspar (Two directions at 90 degrees)
- Amphibole (Two directions NOT at 90 degrees)
- Halite (Three directions at 90 degrees)
- Calcite (Three directions NOT at 90 degrees)
How many crystal structures are there?
6
What makes up a Silica tetrahedron?
4 oxygens, and 1 silicon (fundamental for silicate minerals)
Olivines and Garnets are…
both silicate minerals with isolated tetrahedron (do not share oxygens…instead, bonded by cations)
In single chain silicates, how many basal oxygens are bonded? What is the ratio?
2 of the 3 oxygens are bonded. The Si:O ratio is 1:3
What are double-chain silicates?
two single chains that share oxygens where tetrahedra touch, yielding an Si:O ratio of 2:7
What are sheet silicates?
Share oxygens along the base of the tetrahedra, but not the top. The Si:O is 4:11
What are framework silicates?
all of the oxygens are shared between adjacent tetrahedra, yielding an Si:O ratio of 1:2.
Example of a single chain silicate?
Double chain silicate?
Sheet silicate?
Framework silicates?
Pyroxene (single chain)
Amphiboles (Double chain)
Micas and Clays (Sheet silicate)
Quartz and Feldspar (Framework silicate)
Why are crystal structures limited to six?
Topology
