ROCK TYPE / PROPERTIES Characteristics of IGNEOUS Rock (from molten rock or volcanic fragments) Possible Textures: Glassy Vesicular (full of bubble holes) Or randomly oriented small crystals or randomly oriented large crystals no fossils or organic material. Some Possible Chemistries: Dark colors (rich in magnesium or iron); multicolored (several kinds of mineral crystals are present); light colors (rich in quartz or feldspars); sometimes distinctive minerals are present such as olivine (green) or alkali feldspar (pink). Some 1. 2. 3. Characteristics of SEDIMENTARY Rock (from sediments or precipitation of crystals in water at or near Earth's surface) Some Possible Textures: 1. Clastic or made of rock fragments either large or small such as mud, silt, sand, gravel or pebbles) 2. Parallel layers 3. Fragments of life forms (fossils) Some Possible Chemistries: 4. Often one color (if fine grained); 5. Multicolored if composed of large rock fragments cemented together 6. Sometimes composed of calcite (precipitated by corals or shells) which fizzes when acid is applied; sometimes composed of halite or gypsum (soft light-colored crystalline rocks that form when salty water bodies dry up). Characteristics of METAMORPHIC Rock (from physical or chemical alteration of other rocks by heating or intense pressure beneath Earth's surface) Some Possible Textures: 1. Foliated (folds such that minerals lie parallel to one another) 2. Banded (separate bands of light and dark minerals make wavy folds in the rock -- not like the flat layers in sedimentary rocks) 3. An especially shiny metallic reflection from crystals aligned parallel to one another; may contain very large crystals of equal size; sometimes deformed fossils (stretched or crushed). Some Possible Chemistries: Often contain "metamorphic minerals" such as garnets (reddish-brown 12-sided crystals), mica (flat and shiny gray), and epidote (light green). Rock Type Sedimentary (layers & earthy tones) Rock Color Rocks tend to be tan or grey in color. Rock Compositions Layers visible when broken. Composed of clays, fine grained but not very smooth. Unique Properties When more heat and pressure added ‘morphs’ into slate. Shades of red, oranges, tans, or whites in color. Generally 1 color or layering may show different shades. Usually greys, tans or white in color (Samples containing iron are reddish). Generally 1 color. Grainy/Sandy feeling. Visible grains. Often have visible layers. May contain fossils. Nicknamed ‘Red Rock” Sandstone Medium to fine grained (may see grains w/ naked eye). More coarse to touch. May see layering. Fizzes w/ HCL. May contain fossils. Limestone Very fine grained (cannot see grains). Composed of silts, muds & clays. May feel chalky. May contain fossils. Not foliated (no layers). Medium grained. Medium to coarse grained. Hard rock w/ interlocking quartz crystals. Common parent rock is limestone. Parent rock is sandstone. Quartzite Banding due to alternate layers of different minerals, or different colors. Harder, denser and may be shinier than shale. Parent rock is often granite. Gneiss Shades of tans, greys or creams. Metamorphic Cream or white in color. May show swirls of darker color. White, tan or pink. Can be different colors, mostly black and white, may contain pink, green, or brown. Shades of grey. Rock Name Shale Siltstone Parent rock is shale. When tapped on another rock has higher pitch than shale. Marble Slate Rock Type Igneous Extrusive (no visible crystals) Intrusive (large crystals) Rock Color Black, dark grey. Rock Compositions Glassy texture. No visible grains. Volcanic glass. Fractures look like broken glass. Lighter colors of grey and Very light rock with small to brown. medium sized holes. Sandpaper feel. Generally dark brown, black or Fairly dense with small to medium red. sized holes. Dark in color (blacks & greys) Fined grain and more dense than pumice or scoria. May contain very small or no visible holes. Generally lighter in color, usually Large mineral grains of quartz, mostly black and white feldspar, hornblende and mica. speckled, may also contain pink or brown speckles. Dark in color. Large mineral grains of feldspar, augite and olivine. No quartz crystals. Unique Properties Conchoidal fracture (breaks in a circular pattern) Will float in water. Rock Name Obsidian Pumice Will sink in water. Makes up oceanic plates. Scoria Basalt Parent rock of gneiss. Granite Can be magnetic. Also may contain rare metals like platinum. Gabbro Name Date Period Introduction: Rocks are records of past climates, life, and tectonic processes. In this lab you will describe the physical characteristics of 8-10 rocks and use those characteristics to determine whether the rock is igneous, metamorphic, or sedimentary, its name, and its environment of formation. Part I: Rock Types and Names Directions: Complete the table below describing each of your rock samples. Use your class notes, the Rock Type Properties Key, and the Rock Names Key to determine which type of rock each sample is and its name. Justify your choices for each rock type and name by citing characteristics of the sample that match characteristics in the keys in the evidence columns. Rock # Drawing Description (Color(s), Texture, Crystal presence, size, & shape, unique properties) Type of Rock? (Igneous, Metamorphic, Sedimentary) Evidence Rock Name Evidence Part II: Environment of Formation Directions: Pick 3 of the rocks from your bucket. Research the environments in which these rocks form (Use your class notes, textbook, or other resources). Explain how their characteristics show evidence of their environment of formation. One example has been completed for you. Rock Name Mica Schist Environment of Formation and Evidence Flattened crystals and foliation indicate this rock was exposed to intense heat and pressure that caused partial melting and rearrangement of its crystal grains.