All others2%Notes Lab #1: PHYSICAL PROPERTIES OF MINERALS Earth Lab Chapter 2 Crystal Form/Crystal Habit – the external geometric shape of a crystal which reflects its atomic structure. Luster – how light is reflected from a fresh surface of a mineral, e.g. metallic, sub-metallic, nonmetallic. Hardness – the resistance to abrasion on a fresh surface. Can it be scratched?  See MOHS Hardness Scale’s 10 index minerals (Pg 31, Table 2.3 Earth Lab): Talc is #1 and Diamond is # 10. The first two minerals, Talc and Gypsum, can be scratched with a fingernail. Minerals harder than 6 are harder than a porcelain streak plate (won’t streak). Streak – color of a powdered mineral which is tested by rubbing the mineral across a porcelain streak plate. Color – hue, tint or actual color of a mineral. Not generally diagnostic for minerals, e.g. quartz may be colorless, milky, pink, purple, smoky, etc. Cleavage – the tendency to break along preferred surfaces called cleavage planes. Cleavage planes present flat, light reflective surfaces (surfaces cut with a rock saw are dull). Fracture – the tendency to break along an irregular surface. May appear hackly (rough) or conchoidal (curved and ribbed). Specific Gravity – density. Note high specific gravity of galena, magnetite, pyrite. Effervescence – Acid, such as hydrochloric acid (HCl), applied to CaCO3 causes a “fizzing” reaction. 2H + CO3 → H2O + CO2 (fr om HCl) (from CaCO3) (water) (escaping gas bubbles) Magnetic – attracted by a magnet. Taste – unique flavor: halite tastes like salt. Smell – distinctive odor: sulfurous smell of galena. Feel – distinct physical sensation when touched: silky (talc); greasy (graphite). Double Refraction – ray of light splits in two producing two offset images (Iceland spar calcite). Tenacity – resistance to mechanical deformation (breaking, bending). Some examples: • Brittle - describes most minerals • copper is ductile – can be elongated into wire • gold is malleable – can be shaped and pounded into a thin leaf. Fluorescence – short light waves radiate back as long waves; changes the color of some minerals. _______________________________________________________________________________________________________________ Physical properties of minerals: Mineralogy Society of America Website http://www.minsocam.org/MSA/collectors_corner/id/mineral_id_keyi3.htm Other minerals websites: http://webmineral.com/determin.shtml http://csmres.jmu.edu/geollab/Fichter/Minerals/Minalpha.html http://pubs.usgs.gov/gip/gemstones/Notes Lab #2: ROCK FORMING MINERALS Earth Lab Chapter 3 Major elements in the Earth’s Crust: O oxygen Si 75% silica Al aluminum Fe iron Ca 23% calcium Na sodium K potassium Mg magnesium All others 2% 100% Rock Cycle – the events involving the formation, alteration, destruction and re-formation of the three rock types: igneous, metamorphic, and sedimentary rocks. Geologic processes convert each type of rock into the other two types. Plate tectonics and climate drive the rock cycle processes. The Silicate Ion - the basic building block of all silicate mineral structures. It is a tetrahedron: a pyramidal structure with a central silicon ion (si4+) surrounded by four oxygen ions (O2-), giving the formula SiO4 4- . Because the silicate ion has a negative charge, it often bonds to cations to form electrically neutral minerals. The silicate ion typically bonds with cations such as sodium (Na+), potassium (K+), calcium (Ca+), magnesium (Mg++), and iron (Fe++). Chemical Classification Groups of the Rock Forming Minerals: 1. Silicates - basic chemical building block is the silica tetrahedron (SiO4 ) 2. Non-Silicates: Example: a. Carbonates - Basic unit is CO3…………… calcite CaCO3 b. Sulfates - Basic unit is SO4…………… gypsum CaSO4 · 2H2O c. Sulfides - S plus a metal(s) …………… galena PbS d. Oxides - O plus a metal(s)……………. magnetite Fe3O4 e. Hydroxides - OH plus a metal(s)………….. limonite FeO · OH · nH2O f. Phosphates - Basic unit is PO4 …………… apatite Ca5(PO4)3(F,C.,OH) g. Halides - Halogen ion present ……...... halite NaCl h. Native elements - Occur in elemental form: Ag silver Cu copper Au gold Fe iron Pt platinum C graphite, diamond S sulfur Feldspars - The most abundant group of minerals in the crust. They are framework silicates; however, aluminum has substituted for some of the silicon. In addition to silicon, oxygen, and aluminum the feldspars contain sodium, calcium, or potassium. Feldspars containing potassium are called potassium feldspars or K feldspars (Two K feldspars are microcline and orthoclase). If sodium or calcium, or both, are incorporated into the feldspar crystal structure, then the mineral is plagioclase feldspar.K Na Ca Plagioclase feldspars Orthoclase; Microcline A website for the feldspar minerals: http://www.minerals.net/mineral/silicate/tecto/feldspar/feldspar.htmNotes Lab #3: IGNEOUS ROCKS Earth Lab Chapter 4 Rock Identification The elements present in the Earth are organized into mineral grains, and mineral grains aggregate to form rocks. In lab you learned to identify common rock forming minerals by their physical properties, now you will learn to recognize common rocks. Rocks are mixtures of minerals, held together by relatively weak bonds between individual mineral grains or, in some cases, by cementing materials which act like glue. Classification of rocks is based on the way the mineral grains of the rock crystallize. Igneous rocks are formed by solidification of magma (freezing) or by accumulation of fragments ejected during volcanic eruptions. Sedimentary rocks are formed by the deposition and subsequent aggregation of rock or mineral fragments produced by erosion and transported by wind or water. Some sedimentary rocks form by precipitation of minerals from the dissolved elements present, primarily, in seawater. Metamorphic rocks are formed when existing sedimentary or igneous rocks are subjected to increases in temperature, pressure, or stress, which cause the original mineral grains to