Ch.3: Minerals Flashcards
Mineral
a naturally-occurring, inorganic crystalline solid that has a definite chemical composition and specific physical properties
Crystaline material
a solid having a regular internal atomic
arrangement; may or may not have formed as a crystal
Crystal
a solid having external crystal faces that reflect its internal crystalline structure; crystal faces have a precise geometric arrangement
Rock
an aggregate of one or more minerals; texture (size and
arrangement of mineral grains) indicates the rock’s origin
Igneous Rock
formed from crystallization of molten rock
magma); may be cooled slowly below surface (plutonic/intrusive) or quickly on or near surface (volcanic/extrusive
Sedimentary rock
formed generally from the compaction + cementation of eroded particles, or sediment, in the process of “lithification”
Metamorphic
formed from the recrystallization of preexisting rock due to elevated temperature and pressure
Rock Cycle
magma → crystallization to form igneous rock
→ weathering into sediment → compaction + cementation into sedimentary rock
→ metamorphism into metamorphic rock → melting to form magma (shortcuts
may occur, e.g. metamorphic rock may weather into sediment rather than heat up
enough to melt, etc.)
Polymorphic
same composition; different structures; ex) graphite and diamond
The two polymorphs of carbon (diamond and graphite) are the hardest and softest minerals, a result of different types of atomic bonds.
Rock Texture
arrangement of mineral grains inside a rock, not how smooth or rough it feels) is how we distinguish one type of rock from another
Eurhedral grains
well-formed, crystallized early, with room to grow
Anhedral grains
no crystal faces, grew later, filling in spaces
Element and Atom
Element: pure substance that cannot be separated into other elements
Atom: smallest part of an element that retains the characteristics of that element
Cation vs. Anion
Cation: positively charged ion
Anion: negatively charged ion
Mineral physical properties (8)
Luster: appearance in reflected light; metallic vs. nonmetallic
Color & Streak (color in powdered form)
Hardness: resistance to abrasion; how Mohs’ scale is used
Crystal form: described by number and shape of crystal faces
Cleavage: number of cleavage planes and angle between them
Fracture (irregular, conchoidal): Minerals that have no lattice planes of weakness
Specific gravity (related to density)
Special properties: magnetism; effervescence in HCl acid; striations; iridescence;
fluorescence
Carat vs. Karat
Carat = Diamont 1-100 Karot = Gold out of 24k
Mineral classes based upon the dominant anion:
Silicates SiO2
4- Most rock-forming silicate minerals
Native elements Cu, Au, C Copper, Gold, Graphite, Diamond; most
valuable ore minerals
Si to O ratio
Silicate type Unit Si:O Mineral example
Isolated SiO4 1:4 Olivine
Single chain SiO3 1:3 Pyroxene (augite)
Double chain — — Amphibole (hornblende)
Sheet —- — Mica (biotite, muscovite)
Framework SiO2 1:2 Feldspar (plagioclase, K-feldspar)
Quartz
Ionic bond
transfer of electrons (IT)
Covalent bond
sharing of electron pairs produces harder mineral
Geode
cavity within a rock that can be filled with
well-formed crystals that grew from solution
Cleavage
Cleavage is the tendency for a mineral to break along
lattice planes with weaker atomic bonds.
Cleavage creates flat surfaces that may occur in steps.
Cleavage can be distinguished from crystal faces because
cleavage planes go all the way through a mineral;
crystal faces are only on external crystal surfaces.
Types of cleavage
One direction, or platy
Two directions (or prismatic) at 90°
Two directions (or prismatic) not at 90 °
Three directions at 90 ° or cubic
Three directions not at 90 ° or rhombohedral
Four directions not at 90° or octahedral
Diamonds 4 c’s
1) carat weight
2) color
3) clarity
4) cut:
- Brilliance: the reflection of white light from a stone’s
facets
- Dispersion: also called “fire,” the separation of white light
into the spectral hues
Silicates
- Isolated (or independent) Tetrahedra share no oxygens–
they are linked by cations - Single-chain structures bonded with
Fe and Mg - Double chain of silica tetrahedra bonded together; variety of cations
- Sheet Silicates Muscovite Two dimensional sheets of linked tetrahedra Characterized by one direction of perfect cleavage
- Framework Silicates Potassium Feldspar
All four oxygens in the silica tetrahedra are shared
Are all minerals crystals?
Are all crystals minerals?
No not all minerals are crystals
Yes all crystals are minerals
