Geology recognition exam

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Pyrite
Can't be scratched with fingernail
Can be mistaken for GOLD
Streak: slightly greenish
Crystalizes in isometric system (cubes)

Marcasite
Acid: bubbles
Streak: pure grey
Crystalizes in orthorhombic system (pravoagolnik)

Galena
Crystalizes in isometric hexoctahedral system
Cleavage: good
Streak: black, lead gray
Color: lead gray, silvery
Luster: metalic on cleavge planes
Crystal system: cubic

Fluorite
Streak: white
Luster: vitreous
Crystal system: isometric
May be fluorescencent

Loess
Like sand???????????

Clay shale
Colour: dark grey, greenish, reddish, and brown or yellowish brown
Texture: very fine-grained
Tendency to split into thin layers??????????

Clay stone
Colour: variable: black, white, grey, brown, red, green, blue
Smooth to touch???????????

Haematite
Cleavage: none
Streak: bright to dark red
Colour: metallic grey, dull to dark red
Luster: metallic to splendent
Crystal system: trigonal
Magnetic: yes

Magnetite
Colour: black, grey with brownish tint in reflected sun
Luster: metallic
Streak: black
Cleavage: indistinct, parting on, very good
Isometric crystals
Magnetic: yes

Limonite
Luster: earthy
Color: various shades of brown and yellow
Streak: yellowish brown
Cleavage: absent

Calcitic tufa

Limestone
Colour: yellow, white, or gray
Texture: granular
Soft rock and is easily scratched
Bubbles vigorously when a drop of dilute hydrochloric acid is dropped on it

Quartz
Color: colorless through various colors to black
Cleavage: indistinct
Luster: vitreous – waxy to dull when massive
Streak: white

Calcite
Crystal system: trigonal
Cleavage: perfect on
Colour: typically colourless or white - may have shades of various colours
Luster: vitreous to pearly on cleavage surfaces
Streak: white
With hydrochloric acid the calcium carbonate reacts with the acid and produces carbon dioxide gas, water, and calcium chloride. The carbon dioxide produces the bubbles that you see on the surface of the rock

Aragonite
Color: white, red, yellow, orange, green, purple, grey, blue and brown
Cleavage: distinct on, imperfect
Luster: vitreous, resinous on fracture surfaces
Streak: white
Crystal habit: orthorhombic
Streak: uncolored/ white.
Luster: vitreous, resinous
Cleavage: distinct/ good
Solubility: dilute acid

Magnesite
Color: colorless, white, pale yellow, pale brown, faintly pink, lilac-rose
Cleavage: perfect, but often not seen in cryptocrystalline specimens.
Crystal system: trigonal
Streak: white
Luster: dull, earthy, chalky, vitreous
Can be hard to identify and is often confused with howlite. Effervesces in room-temperature dilute HCl (5%) when powdered. Perfect cleavage if visible.
Crystal System: trigonal

Syenite
The texture of syenites, like that of granite, is granular, and these rocks differ from granite only by the absence or scarcity of quartz
Colour: pale, grey and pink
Fractional crystallization

Granite