Earth Science 11 Corpuz DESCRIPTIONS OF ROCK-FORMING MINERALS

VOCAB Mohs’ scale hardness – hardness of a mineral and scratch resistance. example: 1(soft) – 10 (hard) Streak – color of the minerals powder on a streak plate. example: Iron Pyrite’s color is brass-yellow, but it’s streak is greenish brown. Luster - How does the mineral reflect light? example: Metallic or non Metallic? If non, it is vitreous (glassy), dull (earthy), or waxy (pearly) Color – One mineral can have many colors, and many minerals can have the same color. example: colorless or white

SILCATES The following minerals are made of silica tetrahedron: Quartz Chemical formula = SiO 2 Mohs’ scale hardness = 7 (hardest common mineral) Color = white (pure quartz), colored varieties (pink, purple, brown) Streak = white Luster = glassy Second post abundant mineral Important part of all granites and sandstone

SILICATES Feldspars Most abundant mineral Chemical Formula = Aluminum + other metal Divided into two groups PotashSoda-lime Feldspars Metal = potassium Hardness = 6 Color = white, yellow, gray or pink Streak = white Luster = Vitreous Metal = sodium, calcium Hardness = 6 Color = white, gray, dark green Streak = white Luster = Vitreous

SILICATES Mica Mohs’ scale hardness = Color = colorless, purple, silve, gray, dark green, brown, black Streak = white Luster = pearly, vitreous Flat shiny flakes seen in rocks, granite and gnesis Hornblende Chemical formula = Fe + Mg Mohs’ scale hardness = Color = dark green, brown, black Streak = white/colorless Luster = Vitreous, dull

SILICATES Augite Mohs’ scale hardness = Color = dark green, brown, black Streak = light green Luster = vitreous, dull Olivine Mohs’ scale hardness = 6.5 Color = yellow, yellow-green Streak = colorless Luster = Vitreous Found in some meteorites

SILICATES Garnets Mohs’ scale hardness = Color = dark red, brown, yellow, green, black Streak = colorless Luster = Vitreous Talc Mohs’ scale hardness = 1 Color = white, gray, greenish Streak = white/pale green Luster = waxlike Kaolinite Mohs’ scale hardness = 1 – 2.5 Color = white (pure kaolinite), red, brown, green, blue Streak = white Luster = pearly, dull

CARBONATE MINERALS Found in most lime-stones and marbles Calcite Chemical formula = CaCo 3 Mohs’ scale hardness = 3 Color = colorless to white Streak = white Luster = vitreous, pearly Dolomite Mohs’ scale hardness = Color = white, grey, pink Streak = white Luster = vitreous, pearly

FERROUS MINERALS Magnetite Mohs’ scale hardness = 5.5 – 6.5 Color = black, gray, brownish Streak = black Luster = Metallic Magnetic Pyrite Also known as Fool’s Gold Mohs’ scale hardness = 6 – 6.5 Color = brass-yellow Streak = black with green Luster = Metallic

ASSIGNMENT Questions #6 (Topic Questions) and #4 (General Questions) on pg. 47