Rocks & Minerals Flashcards
What is a rock?
An aggregate of minerals of different kinds in varying proportions; has specific characteristics that permit identification in the field and laboratory
What is a mineral?
A naturally occurring inorganic substance of fairly definite chemical composition whose constituent atoms are arranged in a regular pattern so as to produce a crystalline form
Quartz
*Hardness: 7 (will not streak) Streak: -- *Cleavage/Fracture: Conchoidal *Luster: Vitreous Common Colors: Color-less, white Other: 50-90%of sand and silt fraction in soils; 20-30% in granitic rocks
Orthoclase
*Hardness: 6
*Streak: White
*Cleavage/Fracture: Good in two directions about 90d
Luster: Vitreous
Common Colors: *Flesh pink, grey (micro-cline if deep green)
Other: Common in acidic igneous rocks; mostly in sand and silt; *important source of K
Plagioclase
*Hardness: 6
*Streak: Color-less
*Cleavage/Fracture: Good in two directions 94d
Luster: Vitreous to pearly
Common Colors: Color-less, white, red, grey
Other: Striations on the basal cleavage plane
Muscovite
Hardness: 2-2.5
Streak: Color-less
*Cleavage/Fracture: Good in one direction giving folia
Luster: Vitreous to pearly
Common Colors: Color-less to light yellow
Other: Common in soils weathered from crystalline rocks; common in granites, gneiss, and schists; common in sand fractions and clays
Biotite
Hardness: 2.5-3 Streak: Color-less *Cleavage/Fracture: Folia Luster: Pearly to vitreous *Common Colors: Black, brown, dark green Other:
Calcite
*Hardness: 3
Streak: Color-less
Cleavage/Fracture: Perfect in three directions 75d – forms rhombohedra
Luster: Vitreous
*Common Colors: White colorless or some tint
Other: Occurs in the Ck horizons of arid soils; used to correct soil acidity; *effervesces freely with dilute, cold HCl
Dolomite
Hardness: 3.5-4
Streak: Color-less
Cleavage/Fracture: Perfect in 3 directions 73d
Luster: Vitreous
*Common Colors: Pink, flesh, white
Other: effervesces only slightly with HCl, powder effervesces freely
Apatite
Hardness: 5
Streak: White
Cleavage/Fracture: Conchoidal fracture, poor cleavage in one direction
Luster: Vitreous
Common Colors: Green, it may be brown or red
Other: Only common soil mineral containing phosphorous; occurs in all types of rocks
Olivine
Hardness: 6.5-7
Streak: Pale green to white if any
*Cleavage/Fracture: Conchoidal fracture
Luster: Vitreous
*Common Colors: Olive to grayish-green or brown
Other: usually found as *granular masses; common in basic rocks such as gabbro basalt
Horneblend
Hardness: 5-6
Streak: Color-less
*Cleavage/Fracture: Prismatic at 56d and 124d
Luster: Vitreous or silky
*Common Colors: Black or dark green
Other: *Common in igneous and metamorphic rocks; crystals are like long prisms
Serpentine
Hardness: 2-5
Streak: Colorless
Cleavage/Fracture: COnchoidal fracture often fibrous crystals
*Luster: Greasy
*Common Colors: Variegated greens
Other: Rich source of Mg for plants - may even be harmful
Hematite
Hardness: 5.5 *Streak: Dusky red Cleavage/Fracture: Uneven fracture Luster: Metallic if crystalline Common Colors: Black to reddish-brown Other: Important as iron ore; some can occur in sand and silt fractions
Limonite (“Goethite”)
Hardness: 5.0-5.5 *Streak: Yellow-brown Cleavage/Fracture: -- Luster: -- Common Colors: Dark brown to black Other: Abundant in oxisols, ironstones, and B horizons
Pyrite
*Hardness: 6-6.5
*Streak: Green to brownish-black
Cleavage/Fracture: Uneven fracture
*Luster: Metallic
*Common Colors: Brass yellow
Other: Occurs in all types of rocks but significant in sedimentary rocks or clays associated with coal seams for its acid mine drainage
Gypsum
*Hardness: 2.0
Streak: Colorless
Cleavage/Fracture: Good cleavage in one direction
*Luster: Vitreous, pearly, or silky
Common Colors: Colorless white or grey
Other: Common in soils of arid regions; occurs in sedimentary rocks; used to reclaim sodic soils and as a calcium fertilizer
Syenite
Type: Igneous
Mineralogy: Mostly Orthoclase, small amounts of biotite and hornblende
Texture: Coarse-grained
Other:
Granite
Type: Igneous
Mineralogy: Orthoclase, Quartz, small amounts of plagioclase, biotite, and hornblende
Texture: Coarse-grained
Other:
Rhyolite
Type: Igneous
Mineralogy: Orthoclase, Quartz, small amounts of plagioclase, biotite, and hornblende
Texture: Fine-grained
Other:
Gabbro
Type: Igneous
Mineralogy: Plagioclase, Serpentine (and Augite), small amounts of quartz, and hornblende
Texture: Coarse-grained
Other:
Basalt
Type: Igneous
Mineralogy: Plagioclase, Serpentine (and Augite), small amounts of quartz, and hornblende
Texture: Fine-grained
Other:
Obsidian
Type: Igneous
Mineralogy: Orthoclase, Quartz, small amounts of plagioclase, biotite, and horneblend
Texture: Glassy
Other:
Gneiss
Type: Metamorphic
Mineralogy: Quartz, feldspar, and micas common
Texture: Coarse, medium, fine, granular
Other: Color foliation, little to no cleavage
