Rocks and Minerals

Common Forms/Occurrences: Widely distributed as accessory mineral (all classes of rocks) Useful Identification Test: Soluble in HNO3 or HCl Chemical formula: Ca5F(PO4)3 Crystal System: Hexagonal prisms Colour: Pale green or dark green, brown, blue,…

Key Characteristics: Moderate to high relief, lack of color, low birefringence and uniaxial character are key features 2V: n/a Relief: Moderate to high positive relief Cleavage: Not observed in thin section Colour and Plechroism: Most commonly…

Key Characteristics: Two cleavages intersecting at 87 °, moderate birefringence and inclined extinction are key features 2V: 2Vz = 25 - 70° Relief: High positive relief Cleavage: Cleavages intersect at 87 ° Colour and Plechroism: Grains generally…

Common Forms/Occurrences: Present in most igneous and both regional and contact metamorphic rocks Useful Identification Test: Transparent to translucent Chemical formula: K(Mg,Fe)3(Al,Si3O10)(OH,F)2 Crystal System: Very short prisms that split…

Key Characteristics: Strong brown coloration and plechroism, birds eye and parallel extinction, and high birefringence are diagnostic 2V: 2Vx = 0 - 25° Relief: moderately high positive relief Cleavage: One perfect cleavage Colour and Plechroism:…

Common Forms/Occurrences: Found in limestone, chalk, travertine, and onyx Useful Identification Test: Effervesces in dilute HCl Chemical formula: CaCO3 Crystal System: Prisms, rhombohedrons, or scalenohedrons that break into rhombohedrons Colour:…

Key Characteristics: Relief which changes upon rotation of stage, extreme birefringence, rhombohedral cleavage and lamellar twinning are all diagnostic 2V: n/a Relief: Moderate negative to high positive relief; Relief changes upon rotation of stage…

Key Characteristics: Two cleavages intersecting at 87 °, moderate birefringence and inclined extinction are key features 2V: 2Vz = 25 - 70° Relief: High positive relief Cleavage: Cleavages intersect at 87 ° Colour and Plechroism: Grains generally…

Common Forms/Occurrences: Found in sedimentary strata; Formed secondarily from limestone Useful Identification Test: Will not effervesce in cold dilute acids; Powdered dolomite will however effervesce in warm acids Chemical formula: CaMg(CO3)2…

Key Characteristics: Relief which changes upon rotation of stage, extreme δ, rhombohedral cleavage and lamellar twinning are all diagnostic. Dolomite usually has higher refractive indices than calcite and may be colorless or iron stained where…

Common Forms/Occurrences: Common in dolomites and limestones Useful Identification Test: Soluble in H2SO4 with evolution of HF; slightly soluble in HCl Chemical formula: CaF2 Crystal System: Usually cubes Colour: Colourless, purple, blue, gray,…

Common Forms/Occurrences: In veins associated with other sulfide minerals Useful Identification Test: Decomposed by H2SO4 and by dilute HNO3 Chemical formula: PbS Crystal System: Forms cubes and octahedrons Colour: Silvery gray Streak: Gray to dark…

Common Forms/Occurrences: Two groups classified as Pyralspite and Ugrandite Useful Identification Test: Soluble with difficulty in HF Chemical formula: complex silicate Crystal System: Dodecahedrons Colour: Usually red, black, or brown; sometimes…

Common Forms/Occurrences: Principally occurs in metamorphic rocks ie. Crystalline limestones, schists, and gneisses or in hydrothermal veins Useful Identification Test: Opaque, relatively soft, non magnetic, and foliated Chemical formula: C Crystal…

Common Forms/Occurrences: Found in alabaster, satin spar, and selenite Useful Identification Test: Soft; Shows better cleavage than talc Chemical formula: CaSO4 ? 2H20 Crystal System: Tabular crystals, prisms, blades, or needles Colour: Colourless,…

Key Characteristics: Low negative relief, inclined extinction, low birefringence are key features 2V: 2Vz = 58° Relief: Low negative relief Cleavage: Two cleavages intersect at 42° and 138° Colour and Plechroism: Colorless in thin section Optical…

Common Forms/Occurrences: Occurs as extensive beds and irregular masses formed by evaporation of enclosed bodies of sea water Useful Identification Test: Salty taste; Chemical formula: NaCl Crystal System: Forms cubes and octahedrons Colour:…

Common Forms/Occurrences: Mainly of sedimentary origin Useful Identification Test: May be attracted to a magnet after heating Chemical formula: Fe2O3 Crystal System: Thin tabular crystals or massive Colour: Silvery gray, black, or brick red Streak:…

Common Forms/Occurrences: Widely distributed in mountian belts and deeply eroded shield areas of continental crust Useful Identification Test: Optically negative character and large optical axial angle and extinction angle Chemical formula: calcium…

Key Characteristics: Strong coloration and pleochroism, 2 intersecting cleavages, and diamond shaped basal sections are diagnostic 2V: 2Vx = 35 - 130° Relief: Moderate to high positive relief Cleavage: Two cleavages intersect at 56 ° and 124 °.…

Common Forms/Occurrences: Always of secondary origin resulting from the alteration of other ores or minerals containing iron Useful Identification Test: Hard or soft; Chemical formula: Fe2O3 ? nH2O Crystal System: Amorphous masses Colour: Yellow…

Common Forms/Occurrences: Common constituent of Precambrian iron-formations Useful Identification Test: Attracted to a magnet and can be magnetized Chemical formula: Fe3O4 Crystal System: Octahedrons Colour: Silvery gray to black Streak: Dark gray…

Common Forms/Occurrences: Common K-feldspar of pegmatites and hydrothermal veins; Prominent in granites Useful Identification Test: Demonstrates "tartan" twinning Chemical formula: KAlSi3O8 Crystal System: Translucent prisms with…

Key Characteristics: The mineral's low relief, lack of color and tartan twinning are characteristic. In plagioclase feldspar polysynthetic twinning in two directions can mimic microcline's tartan twinning. However, the polysynthetic…