GEOL 20 sedimentary rocks + minerals quiz (Final Vers.)

CLASTIC/DETRITAL

GRAIN:

size— <1/256mm

shape— very fine

sorting— well-sorted

HCI: NO reaction

CEMENT: calcite

POROUS: yes

MINERAL(S): mostly clay, quartz, feldspars

ENVIRONMENT: continental to marine
OTHER: splits easily, feels chalky-to-smooth

Shale (mudstone)

CHEMICAL/BIOCHEM

GRAIN:

size— 1 - 4mm

shape— “chunky”, granola-like

sorting— poorly-sorted

HCI: reaction

CEMENT: calcite

POROUS: yes

MINERAL(S): calcium (shell fragments)

ENVIRONMENT: marine (shallow reef)
OTHER: looks like oats, made almost entirely of shell fragments

Coquina

CHEMICAL/BIOCHEM

GRAIN:

size— ranges from 1/16 - 2mm

shape— very fine to very coarse

sorting— well-sorted

HCI: reaction

CEMENT: well-cemented, “coarsely crystalline”

POROUS: no

MINERAL(S): calcium carbonate

ENVIRONMENT: continental to intermediate marine
OTHER: waxy

Limestone

CLASITIC/DETRITAL

GRAIN:

size— 1/16mm - 2mm

shape— coarse angular grains

sorting— poorly-sorted

HCI: reaction

CEMENT: calcite

POROUS: yes

MINERAL(S): quartz, feldspar, rock and/or clay

ENVIRONMENT: continental (alluvial fan)
OTHER: feels gritty or sandy, variable grain size

Arkose (feldspar sandstone)

CHEMICAL/BIOCHEM

GRAIN:

size— <1/256mm - 1/8mm

shape— very fine

sorting— well-sorted

HCI: reaction

CEMENT: poorly-cemented by calcite

POROUS: yes

MINERAL(S): calcium, clay minerals

ENVIRONMENT: intermediate marine (continental slope/rise)
OTHER: very soft and light earthy rock, white to light brown

Chalk

CHEMICAL/BIOCHEM

GRAIN:

size— micro-crystalline

shape— conchoidal fracture

sorting— well-sorted

HCI: NO reaction

CEMENT: silica

POROUS: low

MINERAL(S): quartz, chalcedony, flint, opal, etc.

ENVIRONMENT: deep marine (abyssal plain)
OTHER: scratches glass, hard and waxy feel

Chert

CLASTIC/DETRITAL

GRAIN:

size— 1/256mm - 1/16mm

shape— very fine

sorting— well-sorted

HCI: likely reaction

CEMENT: calcite

POROUS: low

MINERAL(S): quartz, feldspar, rock and/or clay fragments

ENVIRONMENT: continental (lake) to marine (continental slope/rise)
OTHER: feels chalky, does not split along layers (non-fissile)

Siltstone

CHEMICAL/BIOCHEM

GRAIN:

size— <1/256mm - 1mm

shape— very fine

sorting— poorly-sorted

HCI: NO reaction

CEMENT: poorly-cemented

POROUS: yes

MINERAL(S): fossilized diatoms, quartz, chalcedony, flint, opal, etc.

ENVIRONMENT: deep marine (abyssal plain)
OTHER: very soft and light earthy rock, white to light brown, similar to chalk

Diatomite

CLASTIC/DETRITAL

GRAIN:

size— >2mm gravel

shape— rounded grains

sorting— poorly-sorted

HCI: reaction

CEMENT: calcite

POROUS: yes

MINERAL(S): quartz, feldspar, rock and/or clay minerals

ENVIRONMENT: continental (river/stream channel)
OTHER: very chunky, generally poorly sorted fragments

Conglomerate

CLASTIC/DETRITAL

GRAIN:

size— >2mm

shape— angular grains

sorting— poorly-sorted

HCI: NO reaction

CEMENT: calcite

POROUS: yes

MINERAL(S): quartz, feldspar, rock and/or clay minerals

ENVIRONMENT: continental (alluvial fan)
OTHER: very chunky like conglomerate but sharper/more angular, generally poorly sorted fragments

Breccia

CLASTIC/DETRITAL

GRAIN:

size— 1/16mm - 2mm

shape— gritty/sandy

sorting— well-sorted

HCI: NO reaction

CEMENT: quartz

POROUS: yes

MINERAL(S): quartz, feldspar, rock and/or clay fragments

ENVIRONMENT: continental (river/stream channel)
OTHER: asymmetrical ripplemarks

Quartz sandstone

CHEMICAL/BIOCHEM:

GRAIN:

size— crystalline to micro-crystalline

shape— coarse fossils

sorting— poorly-sorted

HCI: reaction

CEMENT: well-cemented

POROUS: yes

MINERAL(S): calcite

ENVIRONMENT: marine (shallow reef)
OTHER: fossils present

Fossliferous limestone

CLASTIC/DETRITAL:

GRAIN:

size— 1/16mm - 2mm

shape— gritty/sandy

sorting— poorly-sorted

HCI: reaction

CEMENT: well-cemented, calcite

POROUS: yes

MINERAL(S): quartz, feldspar, rock and/or clay minerals

ENVIRONMENT: marine (shallow inner shelf)
OTHER: fossils present

Fossiliferous sandstone

CLASTIC/DETRITAL:

GRAIN:

size— 1/16mm - 2mm

shape— uniform grain

sorting— poorly-sorted

HCI: possibly

CEMENT: well-cemented

POROUS: low

MINERAL(S): quartz, feldspar, rock and/or clay minerals

ENVIRONMENT: marine (continental slope/rise)
OTHER: angular grains

Graywacke

• Mohs hardness of 3

• feels light

• in crystalline varieties, a vitreous luster.

• Color is white or none, though shades of gray, red, orange, yellow, green, blue, violet, brown, or even black can occur when the mineral is charged with impurities.

• non-90° angles

calcite

• white, colorless or gray in massive form, crystals are clear, transparent to translucent. If impurities are present, gypsum may also appear to be red, brown or yellow.

• hardness 2 (very soft), feels light

• Crystals are vitreous (glass-like) to pearly, massive form is dull.

• white streak

gypsum

• is literally salt (NaCl), is salty

• white to light pink or tan

• vitreous (glassy) luster

• white streak

• 2.5 hardness (soft), feels light

Halite

• Purple, lilac, golden-yellow, green, colourless, blue, pink, champagne, brown.

• hardness 4 (scratched by copper penny)

• vitreous & dull luster

• can be crystalline with octahedral faces

Fluorite

• 6.5 - 7 hardness (steel nail)

• white, gray, blue, pink, yellow, brown, and red.

• very waxy and dull luster

• conchoidal fracture

• slightly translucent to opaque

Chalcedony

• Yellow, sulphur-yellow, brownish or greenish yellow, orange, white

• colorless streak

• 1.5 - 2.5 hardness (very soft)

• resinous, greasy or soapy

Sulfur

• metallic

• 1 - 2 hardness (very soft)

• dark-grey to black

• dark-grey to black streak

• Greasy feel; Smudges easily

Graphite

• can vary from white to pale green, gray, or even colorless

• Greasy, waxy, pearly luster

• 1 hardness (extremely soft)

• excellent basal cleavage

Talc

• dark red to reddish brown being the most common, but varieties may be red-violet, brown, black emerald green, or even white.

• 6.5 - 7.5 (very hard, steel nail scratches)

• Luster is vitreous (glass-like) to resin-like, transparent to translucent.

Garnet