rock example samples please review the following terms. be able to see how to relate to our rock...
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Rock Example Samples
• Please review the following terms. Be able to see how to relate to our rock example samples
• Cleavage- a mineral’s ability to split easily along flat surfaces
• Foliation- term used to describe metamorphic rock whose grains are arranged in parallel layers
• Hardness- can be used for identification purposes
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Mohs Hardness Scale
• HARDNESS SCALE
• The hardness of a stone is one of the properties that contribute to identification. Hardness is also an attribute which is important to be aware of, because it may determine what a stone may be used for (jewelry, carving, faceting, handling, storage, etc.) You may want to familiarize yourself with the Mohs Scale of Hardness. This will help you understand the relationships between stones according to their hardness.
The Mohs Scale of Hardness consists of 10 classifications, 1 being the softest, and 10 being the hardest.
• The only mineral that is an exception to this is mercury, which is liquid. To give you a few reference points, the diamond is of course the hardest, rated 10. Your fingernail is a 2, a pocket knife is about a 5-6, and a piece of glass is a 6-7.
• Each classification will scratch the one preceding it. As you know, a diamond (10) will scratch glass (6-7). This technique is commonly used in the field for initial identification, and it is good to have samples of some of these stones with you in order to perform the test. Some minerals have varying hardness according to the direction you may scratch them in, but typically this is either hardly detectable or an exception to the rule. The following, is a partial listing of stones and their hardness classification:
Igneous Rocks
• Examples (5)
Granite Obsidian Scoria Basalt Perlite
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Igneous Rock Samples
Granite
Coarse grainedLight coloredIntrusive
The most abundant intrusive rock
Obsidian
Glassy texture. Formed from cooling lava
Igneous Rock Samples
Scoria
Like pumice rockDark-colored, vesicular Extrusive igneous rock
BasaltThe most common extrusive rock
Formed from the rapid cooling of basaltic lava
Usually grey to black in color, but rapidly weathers to brown or rust-red
Pumice
Igneous Rocks
• Perlite
• Expanded perlite is used as insulation, in lightweight concrete, as an additive in soil (such as an ingredient in potting mix),
Sedimentary Rocks
Breccia ShaleLimestone CoalSandstone Rock Salt (Halite)Conglomerate
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Sedimentary Rocks
• Breccia Breccia and conglomerate are very similar rocks. They are both clastic sedimentary rocks composed of particles larger than two millimeters in diameter. The difference is in the shape of the large particles. In breccia the large particles are angular in shape but in conglomerate the particles are rounded. This reveals a difference in how far the particles were transported.
Sedimentary Rocks
• Shale Shale breaks into thin pieces with sharp edges. It occurs in a wide range of colors that include: red, brown, green, gray, and black. It is the most common sedimentary rock and is found in sedimentary basins worldwide.
Sedimentary Rocks
• Limestone
Most limestone form in shallow, calm, warm marine waters.
When these animals die their shell and skeletal debris accumulate as a sediment that might be lithified into limestone.
Sedimentary RocksCoal
Sedimentary Rocks
The formation of natural diamonds requires very high temperatures and pressures. The conditions occur in limited zones of Earth's mantle about 90 miles
Since coal is formed from terrestrial plant debris and the oldest land plants are younger than almost every diamond that has ever been dated, it is easy to conclude that coal did not play a significant role in the formation of Earth's diamonds.
Sedimentary Rocks
• Sandstone
Sandstone is a clastic sedimentary rock made up mainly of sand-size weathering debris.
Environments where large amounts of sand can accumulate include beaches, deserts, flood plains and deltas.
Sedimentary Rocks
• Conglomerate
The rounded shape of the particles reveal that they were tumbled by running water or moving waves.
Sedimentary Rocks
• Rock Salt is a chemical sedimentary rock that forms from the evaporation of ocean or saline lake waters.
• It is also known by the mineral name "halite". It is rarely found at Earth's surface, except in areas of very arid climate.
• It is often mined for use in the chemical industry or for use as a winter highway treatment.
• Some halite is processed for use as a seasoning for food.
Metamorphic Rocks
Gneiss Schist QuartziteMarble Slate Phyllite
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Gneiss or Schist
Schists are less coarsely crystallized and more prone to cleaving into flakes or slabs.
Gneiss has layers of light-dark bands differing in mineralcomposition. Has coarser grainthan schist
Metamorphic Rock
• Quartzite
• Quartzite is a non-foliated metamorphic rock
• Produced by the metamorphism of sandstone.
• It is composed primarily of quartz.
Metamorphic Rock
• Marble
• Marble is a non-foliated metamorphic rock
• Produced from the metamorphism of limestone.
• It is composed primarily of calcium carbonate.
Metamorphic Rock
• Slate
• Forms from shale
• Used as roofing and floor tiles
• Slate forms when sedimentary rock becomes involved in a convergent plate boundary
Metamorphic RockPhyllite
Phyllite is a foliate metamorphic rock that is made up mainly of very fine-grained mica.
The surface of phyllite is typically lustrous and sometimes wrinkled.
It is intermediate in grade between slate and schist