Mineral Identification Flashcards
Mineral Definition
- naturally ocurring, inorganic, crystalline solid with a definite, but sometimes variable chemical composition
- must form in nature
- man-made crystals are not minerals (cannot tell them apart)
Solids
- must be solid (liquids and solid are not minerals, mercury)
Naturally Occurring
- must form in nature
- man-made crystals are not minerals (cannot tell them apart)
Inorganic
- must be inorganic (no organic compounds, C bonded to H, not formed by living organisms)
- Coal is made from previously living organisms
- Can have carbon and not be organic
- Some animals can manufacture biochemical minerals to make shells and hard parts (made by animals but are not organic)
Crystalline
- Minerals have atoms in a specific, orderly pattern or framework called a crystal lattice (have a distinct shape, quartz)
- Non-minerals have atoms or molecules in an amorphous solid are randomly arranged (no distinct shape, volcanic glass)
Chemical Composition
- a definite but sometimes variable chemical composition
- each mineral has a set chemical composition (mixture of elements), although some elements may be swapped for other elements (dark vs white chocolate chip cookie)
- do not use colour to identify
Colour
- highly variable among samples of the same mineral
- colours vary due to impurities in the crystal structure, microscopic inclusions of other minerals, or heat
- use only as a guide
Lustre
- describes how a mineral reflects light
- metallic, vitreous (glassy), earthy, pearly
Clarity
- ability to transmit light
- opaque, translucent, transparent
Streak
- colour of the powdered mineral
- scraping rock along a porcelain “streak plate”
Habit
- determined by chemistry
- shape a crystal will naturally develop as it grows (atoms added)
- cubic, prismatic, fibrous, platy, granular, massive (shapeless)
- mineral has a lot of space when growing, tend to form perfect crystals, limited shape = more irregular crystals)
Euhedral
well formed crystal faces
Subhedral
some crystal faces
Anhedral
lacking crystal faces
Fracture
- how a mineral breaks
- irregular fracture (rough, uneven) = Feldspar
- conchoidal fracture (circular depression) = Obsidian
Cleavage
- some minerals break along naturally existing planes of weakness called cleavage planes
Platy Cleavage
muscovite
Cleavage in 2 directions at 90*
feldspar
Cleavage in 2 directions not at 90*
Amphibole/hornblende
Cleavage in 3 directions at 90*
halite
Cleavage in 3 directions not at 90*
calcite
Hardness
Fingernail (2.5), Copper penny (3.5), Knife blade (5.5), Streak plate/ steel nail (6.5)
Earth Minerals
- naturally occurring materials that make up the Earth’ crust
- minerals, rocks, fossils, soil
Minerals VS Rock
- minerals consist of a single crystal
Rock
- most rocks consist of many minerals, fossils or soils
- granite (quartz, potassium feldspar, biotite, plagioclase)
- rocks are solid aggregates of earth materials (soil - mudstone)
Aggregate of Earth Materials
soil - mudstone
Aggregate of Crystals
built entirely out of whole, unbroken minerals only (granite)
Aggregate of Grains
built out of fragments of other rocks, minerals or fossil
(conglomerate)
Classifying Earth Minerals
Form and composition
Form
aggregate of crystals
aggregate of grains
single crystal
amorphous
Composition
HOMOGENEOUS (made up of single type of mineral or earth material, volcanic glass)
HETEROGENEOUS (made up of several different types of minerals or earth materials, granite)
ORGANIC (made up of organic compounds, coal)
INORGANIC (made up of inorganic compounds, granite)
