Lecture 4 - Rocks and Minerals

Lecture 4

Define mineral

Natural, inorganic, crystalline, definite homogeneous chemical composition.

how much of the crust are made up of silicates

92% (feldspars are most common group)

Intrusive Igneous Rocks

Slow formation, deep, big crystals

Extrusive Igneous Rocks

Rapid formation, surface, small crystals, explode outa volcanos

how are sedimentary rocks formed

Weathering → erosion → Transportation → Deposition → burial → Lithification

what percent of the immediate surface is sedimentary rocks

80%

Clastic rocks

Sedimentary, rock fragmants (ex. sandstone or shale)

Chemical/biogenic

precipitation or carbon from biological processes (ex. like limestone or halite)

conditions of forming metamorphic rocks

solid-state recrystallization at 10km deep and temp 200-800 degrees Celsius. Does not completely melt.

Regional Metamorphic Rocks

High T+P, Foliation (layers), mountains, ex gneiss, schist.

Contact Metamorphic Rocks

High Temp from nearby magmatic intrusions, ex. marble.

How are minerals formed?

crystallization from a liquid (melting), diffusion from solid, precipitation of water (a solution), weathering, crystallization from a gas, and biomineralization. (NOT elastic strain or organic mater)

What type of rocks to igneous rocks involved in mountain building turn into?

Metamorphic

Define cleavage

tendency of minerals to break in persistent planes. NOT in all minerals.

List igneous rock composition categories and give examples.

[DARKEST] Ultra Mafic (Peridotite+Kimberlite) Mafic (Basalt+Gabbro) Intermediate (Diorite+Adesite) Felsic (Granite+Rhyolite) [LIGHTEST]

what is the CO gemstone

Aquamarine (blue)

What is the CO mineral

Rhodochrosit (red)

How is ore formed

Many ores form in hydrothermal veins, where hot water descending into fractures is heated by magma and ascends, depositing sulfides, silicates, and native elements like gold and silver

what are placer deposits

Placer deposits are concentrations of heavy minerals (like gold) in stream beds, which were heavily targeted during early mining history like panning in the Platte River

What chemicals make it blue

Iron and Titanium

What chemical makes it red

Chromium

What are diamonds graded based on

Color, Cut, Clarity, Carrat

What is the largest diamond ever found?

Cullinan diamond found in South Africa in early 1900s. 3106carrats. made into the crown jewels.