ERTH1501 WK2

Most abundant elements in Earth and crust

Fe, O, Si, Mg

Fe, O, Si, Mg, Al, Ca, K, Na

Calcite (CaCO3)

Hardness = 3

Rhombohedral cleavage

Can form by direct precipitation from seawater or heated fluids in the Earth’s crust

a drop of diluted HCl on calcite produces an instant, obvious fizz

Dolomite CaMg(CO3)2

Hardness = 3

Rhombohedral cleavage

a drop on dolomite produces slow or no obvious bubbling

Aragonite CaCO3

Can form by direct precipitation from seawater or heated fluids in the Earth’s crust

Limestone + Dolostone

Calcite and aragonite

Dolomite

Oxide: Magnetite (Fe3O4)

contains both 2+ and 3+ Fe

alters easily to hematite in more oxygen-rich environments, so rocks that once contained magnetite may be altered to contain hematite instead.

a dark grey – black streak. is magnetic

Oxide: hematite (Fe2O3)

contains only the 3+ type of Fe.

forms in environments that are more oxygen-rich than magnetite

will have a red-brown streak

Examples of carbonates

Examples of halides

Examples of oxides

Examples of sulfides

Examples of sulfates

Examples of native elements

Silica tetrahedra

Isolated tetrahedra

Single chain silicate

Double chain silicate

Sheet silicate

Framework or Network silicate

Framework or Network Silicate - Feldspars

PLAGIOCLASE FELDSPAR: NaAlSi3O8 to CaAl2Si2O8
POTASSIUM (K) FELDSPAR (aka Microcline Orthoclase) KAlSi3O8

Characteristics:
- Feldspar: 2 cleavages, striated appearance

Feldspar classification