Examples of this rock type include basalt and obsidian. Here's a chart of some of the key characteristics that can help you identify the rocks within these three main classes.
Crystals Small, flat surfaces that are shiny or sparkly, like tiny mirrors. Fossils Imprints of leaves, shells, insects, or other items in the rock. Gas bubbles "Holes," like Swiss cheese, in the rock. Glassy surface A shiny and smooth surface, like colored glass. Ribbonlike layers Straight or wavy stripes of different colors in the rock. Sand or pebbles Individual stones, pebbles, or sand grains visible in the rock.
Each type of rock has characteristics that make it special and unique, and no two rocks are exactly the same. The three main types of mysterious rocks are Igneous, Sedimentary and Metamorphic rocks.
As a geologist, it is their job to unlock the mystery behind the rock. Igneous rocks are formed when liquid magma cools and hardens either inside the earth under the crust, or outside the earth after a volcano has erupted. When the magma cools slowly deep below the earth's crust, crystals form and the rock becomes course and grainy with pockets of "air bubbles". When the magma cools rapidly closer to the earth's surface or outside the surface after an eruption, the crystals that form are smaller and a fine grain rock is formed.
Igneous rocks can take on a variety of disguises because of all the different possible chemical make-ups of magma and the different cooling rates that the magma hardens at. Geologists have to give igneous rocks a deeper look to really determine what type of rock it is. Sedimentary rocks are the "regular Joes" of rocks. These types of rocks are formed as sediments; such as sand, pebbles, minerals, plants or animals, and are moved together by a force like water.
Over time, the sediments form layers and harden into rock. This formation process can lead to the creation of fossils. Fossils form when a plant, animal, or track is captured in the layers of the rock and are preserved forever. Some of the sedimentary rocks are held together by an electrical attraction, while others remain loose and brittle.
This type of rock can be characterized by distinct layers of rock that run parallel to each other and can even look like stripes. Generally, the rocks are fairly soft and can break apart or crumble easily. Examples include limestone, flagstone or sandstone. Holing these samples up to the light and slowly turning them will reveal a slight sparkle.
Origin of your Samples : Madoc, Ontario Uses : Marble is used for construction, countertops, and carvings, and may be a source for magnesium. Rock Type: metamorphic Composition: recrystallized quartz grains Original Rock: sandstone Environment: Quartzite forms at many temperatures and pressures. Distinguishing Characteristics: light grey or white, medium grained, very hard. Origin of your Samples: Badgeley Island, Ontario Uses: Quartzite is the raw material for the glass and ceramics industries.
Lava can explode out of a volcano and make pumice or ash, or flow down its side and make thick layers of fine grained rock or volcanic glass. Distinguishing Characteristics: Very fine grained, pinkish-grey, sometimes with dark streaks. If dipped in water and rubbed on a piece of paper, rhyolite will likely tear the paper rather than leave a muddy streak. Origin of your Samples: Timmins, Ontario Uses: Black volcanic glass called obsidian and frothy-looking white coloured rock called pumice are other forms of rhyolite.
Pumice is used in abrasives, concrete, stone-washing laundries, hand soap, emery boards, and sandpaper and is used in sandblasting. Rock Type: sedimentary Composition: grains of sand that can be feldspar or quartz - the amount of other minerals, such as mica, depend on how much weathering has occurred. Environment: Already existing rocks are eroded and the grains are transported and sorted by rivers.
The resulting sand is deposited on beaches, along floodplains or in deltas, where it is eventually buried by other sediments. This causes a slow squeezing of the sediments.
As the sediments are compacted, fine clay helps to fuse the larger particles together. The sediments are also cemented by chemicals left by the water in the original sediment.
The presence of sandstone indicates that there was water with fairly high energy waves on a beach or a fast moving river Distinguishing Characteristics: Coarse to very fine grains, beige to grey colour, feels like sandpaper. Origin of your Samples: Georgetown, Ontario Uses: Sandstone is used for flagstone to line your walkway or patio. It is also an important building stone.
Rock Type: sedimentary Composition: grains of clay Environment: Shale sediments are deposited in still water low energy such as a lake or a deep, slow river. Distinguishing Characteristics: dull, reddish- brown, very fine grains smooth to the touch , breaks easily. If an edge is dipped in water and drawn along a surface, shale will leave a muddy streak.
Origin of your Samples: Aldershot, Ontario Uses: This shale is the raw material for the brick manufacturing industry in Ontario. Rock Type: metamorphic Composition: clay minerals Original Rock: shale Environment: Slate forms from the heat and pressure when shale is buried deep in the crust. The depth of burial to make slate out of shale is about 10 km. Distinguishing Characteristics: dark grey to black, very fine grains smooth to the touch , harder than shale, distinct layers are visible.
In the past, slate was used as chalkboards. About Us. Indigenous Programs. School Programs. Outreach Programs. School Programs - Students. Field Trip Subsidy Application Procedures.
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