Lab 4 // Sedimentary Rocks

Question 1

conglomerate

Answer 1

Composition: a mix of fragment types, including abundant dark fine-grained rocks (basalt probably)
Properties: gravel mainly with smaller grains such as sand, poorly sorted, well rounded grains
Rock Type: detrital

Question 2

quartz sandstone

Answer 2

Composition: almost entirely quartz grains (the red sandstone has clear quartz grains with red iron oxide cement)
Properties: sand size grains, well rounded grains, well sorted
Rock Type: detrital

Question 3

arkose (a sandstone)

Answer 3

Composition: lots of quartz and lots of potassium feldspar ( + a few dark grains of amphibole and biotite)
Properties: sand and gravel size grains, angular to subrounded grains, poorly or moderately sorted
Rock Type: detrital

Question 4

lithic sandstone

Answer 4

Composition: lots of quartz but also lots of dark, dull grains (likely fragments of fine-grained rocks such as basalt)
Properties: sand and gravel size grains, angular to subrounded grains, moderately sorted
Rock Type: detrital

Question 5

shale (fissile)

mudstone (nonfissle)

Answer 5

Composition: grains too small to see
Properties: mud (silt and/or clay)
Rock Type: detrital

Question 6

chalk

Answer 6

Composition: calcite (chalk is made from the microscopic calcium carbonate shells of plankton)
Properties: fine-grained earthly feel, very soft…can write with it lie chalkboard chalk
Rock Type: biochemical

Question 7

oolitic limestone

Answer 7

Composition: calcium carbonate ooids (tiny fragments are rolled around tin the waves and gather CaCO3 as it precipitates and settles to the seafloor)
Properties: oolithic texture
Rock Type: chemical

Question 8

micrite

Answer 8

Composition: calcite
Properties: very fine grained (microcrystalline texture)
Rock Type: biochemical or chemical

Question 9

coal

Answer 9

Composition: organic carbon (made from the compressed, partially decomposed remains of plants)
Properties:shiny and black, light in weight, conchoidal fractures
Rock Type: biochemical

Question 10

chert

Answer 10

Composition: fine-grained quartz
Properties: very fine-grained quartz (cannot see individual grains = microcrystalline texture), conchoidal fractures
Rock Type: chemical