Kinds of Rocks

[lpetrich]

Geologists have given a large number of individual names for kinds of rocks and minerals, but there are some patterns in them that I wish to present.

There are three main kinds of rocks, igneous, sedimentary, and metamorphic.

I first discuss igneous rocks, rocks that solidified from a molten state: magma (underground) or lava (above ground)
Igneous Rocks, Igneous Rock Classification | CK-12 Foundation, Slide on Igneous Rocks
[TABLE="class:grid"]
[TR]
[TD][/TD]
[TD]Intrusive[/TD]
[TD]Extrusive[/TD]
[TD]SiO2[/TD]
[TD]Fe, Mg[/TD]
[TD]Color
[/TD]
[TD]Dens
[/TD]
[TD]Temp
[/TD]
[/TR]
[TR]
[TD]Solidified[/TD]
[TD]In place[/TD]
[TD]After flowing out[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Solidification rate[/TD]
[TD]Slow[/TD]
[TD]Fast[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Grain size[/TD]
[TD]Large[/TD]
[TD]Small[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Ultramafic[/TD]
[TD]Peridotite[/TD]
[TD]Komatiite[/TD]
[TD]<45%[/TD]
[TD]High[/TD]
[TD]Dark
[/TD]
[TD]High[/TD]
[TD]1600 C
[/TD]
[/TR]
[TR]
[TD]Mafic[/TD]
[TD]Gabbro[/TD]
[TD]Basalt[/TD]
[TD]45-52%[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Intermediate[/TD]
[TD]Diorite[/TD]
[TD]Andesite[/TD]
[TD]52-63%[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Intermediate-Felsic[/TD]
[TD]Granodiorite[/TD]
[TD]Dacite[/TD]
[TD]63-69%[/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[TD][/TD]
[/TR]
[TR]
[TD]Felsic[/TD]
[TD]Granite[/TD]
[TD]Rhyolite[/TD]
[TD]>69%[/TD]
[TD]Low[/TD]
[TD]Light
[/TD]
[TD]Low[/TD]
[TD]800 C
[/TD]
[/TR]
[/TABLE]
Dens = density, Temp = melting-point temperature. The higher the temperature, the more fluid the lava. Komatiite was mostly produced during the Archean, when the Earth's interior was significantly hotter than today.

Sedimentary rocks are formed by deposition of their materials.

• Clastic - produced from small fragments. It is the most familiar kind.
  • Eroded bits of rock - sandstone, siltstone, mudstone / shale, conglomerate
  • Shells - limestone
  • Volcanic eruptions - tuff, breccia
• Condensed or precipitated - evaporites and the like
• Biological - coal

Metamorphic rocks are formed by subjecting existing rocks to heat and pressure. Most metamorphic rocks get that way from being buried by other rocks, but there is a kind called "shock metamorphism" that is produced by impacts of extraterrestrial objects. It's like the rock was hit with a super hammer blow.

 

[lpetrich]

Minerals, like rocks, have oodles of individual names. But here also, there are patterns.

List of Minerals - very good page
Types of Minerals

Native minerals: minerals of a (relatively) pure element

• Metallic: Group 11 elements: Cu, Ag, Au
• Nonmetallic: C allotropes: amorphous, graphite, diamond

• "Amorphous" carbon is often polycrystalline, and not necessarily true amorphous or glassy carbon
• Graphite is composed of graphene sheets, sheets of carbon atoms in hexagonal grids
• Diamond is carbon atoms with neighbors in a tetrahedral pattern

Ionic compounds: anion (negative ion) + cation (positive ion). Ionic-compound minerals almost always have metals and semimetals as their cations, like Na, K, Mg, Ca, Fe, Al, Si. For anions, they often have:

• Oxide: O
• Sulfide: S
• Halides: F, Cl, Br, I -- fluoride, chloride, bromide, iodide
• Hydroxide: OH
• Borate: BO3
• Carbonate: CO3
• Silicate: SiO4
• Phosphate: PO4
• Arsenate: AsO4
• Sulfate: SO4

A mineral may contain significant amounts of two or more cations, two or more anions, or both.

Metal silicates are further divided by their crystalline structure. In particular, how their silicate ions are joined. Silicate ions have a tetrahedral structure, with the silicon atom in the center and the oxygen atoms at the vertices. Silicate ions may share the oxygens in their vertices.

• Framework silicates (tectosilicates) -- all vertices shared; ions form 3D structure
• Sheet silicates (phyllosilicates) --
• Chain silicates (inosilicates) -- single or double chains
• Disilicates (sorosilicates) -- bowtie pairs
• Ring silicates (cyclosilicates) -- rings of 6 ions, stacked in columns
• Orthosilicates (nesosilicates) -- ions separate

Finally, covalent compounds. The main ones are hydrocarbons, in crude oil and tar.