THE BIG 2O MINERALS:
-
1.QUARTZ : Quartz Physical Properties
Chemical Classification Silicate
Cleavage
None – typically breaks with a conchoidal fracture
Mohs Hardness
7
Specific Gravity 2.6 to 2.7
Diagnostic Properties Conchoidal fracture, glassy luster, hardness
Has chem. Form. Of SiO2
A conchoidal fracture refers to a haphazard mode of breakage of a material that does not
adhere to any fixed or well-described physical planes of separation. Brittle materials are
more likely to exhibit conchoidal fracturing
2.ALKALI FELDSPAR
Chemical Classification Silicate
Mohs Hardness 6 to 6.5
Specific Gravity 2.5 to 2.8
Diagnostic Properties Perfect cleavage, with cleavage faces usually intersecting at or close to 90
degrees. Consistent hardness, specific gravity and pearly luster on cleavage faces.
KAlSi 3O 8 – NaAlSi 3O 8 – CaAl 2Si 2O 8
3.MAGNETITE
Mohn’s Scale : 5.5 to 5.6
Has chem. Fom, of Fe₃O₄
Cleavage: Indistinct, parting on, very good
Color: Black, gray with brownish tint in reflected sun
Streak: Black
Luster: Metallic
Fracture: Uneven
Lodestone: Magnetic with definite north and south poles
Specific gravity: 5.17–5.18
4.AMPHIBOLE
Chemical Classification Silicate
Mohs Hardness 5 to 6
Specific Gravity 2.9 to 3.5 (varies depending upon composition
Diagnostic Properties Cleavage, color, elongate
habit…Chemical Composition (Ca,Na) 2–3(Mg,Fe,Al)5(Al,Si)8O22(OH,F)2
What colors are amphibole?
Identification: Typically, amphiboles form as long prismatic crystals, radiating sprays and fibrous
aggregates. They are generally dark coloured though their colours can range from colourless to
white, green, brown, black, blue or lavender. This property is related to composition, particularly
iron content
5.BIOTITE
Properties of Biotite
It is a black mica with perfect cleavage and a vitreous luster on the cleavage faces. When biotite is
separated into thin sheets, the sheets are flexible but will break upon severe bending. When held
up to the light, the sheets are transparent to translucent with a brown, gray, or greenish color.Has
hardness ranging at about 2.5 to 3.has specific gravity ranging at about 2.7 to 3.1--Has a chemical
form of K(Mg,Fe)2-3Al1-2Si2-3O10(OH,F)2
6.CALCITE :
The diagnostic properties of calcite include a defining Mohs hardness of 3, a specific gravity of 2.71
and, 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.
CaCO3
7.PYRITE(FOOLS’S GOLD)
Pyrite is a brassy-colored mineral featuring a metallic luster resembling gold. Pyrite has a chemical
composition of iron disulfide (FeS2) and is the most common sulfide.
Physical Properties of Pyrite
Chemical Classification Sulfide
Mohs Hardness 6 to 6.5
Specific Gravity 4.9 to 5.2
Diagnostic Properties Color, hardness, brittle, greenish black streak, specific gravity
8.CHALCOPYRITE
It has the chemical formula CuFeS2 and crystallizes in the tetragonal system. It has a brassy to
golden yellow color and a hardness of 3.5 to 4 on the Mohs scale. Its streak is diagnostic as green
tinged black.
9.GYPSUM
Gypsum Physical Properties
Color
Colorless to white; may be yellow, tan, blue, pink, brown, reddish brown or gray
due to impurities
Diaphaneity
Transparent to translucent
Mohs Hardness 2
Specific Gravity 2.31–2.33
Diagnostic Properties Transparent and bladed crystals Alabaster Fine-grained, slightly colored
10.FLOURITE
Fluorite (also called fluorspar) is the mineral form of calcium fluoride, CaF2. It belongs to the
halide minerals. It crystallizes in isometric cubic habit, although octahedral and more complex
isometric forms are not uncommon.
The Mohs scale of mineral hardness, based on scratch hardness comparison, defines value 4 as
fluorite.
Colorless, although samples are often deeply colored owing to impurities; Purple, lilac, goldenyellow, green, blue, pink, champagne, brown.
Crystal habit Well-formed coarse sized crystals; also nodular, botryoidal, rarely columnar or
fibrous; granular, massive