Can be white, pink, or gray in color and at least 20% of quartz.
Forms when molten rock cools very rapidly.
Texture is glassy
Obsidian is a naturally occurring volcanic glass formed as an igneous.
Forms during explosive volcanic eruptions
Has a rough texture.
Is an igneous rock.
Volcanic rock of felsic.
is a common extrusive igneous rock formed from the rapid cooling of ballistic lava exposed at or very near the surface of a planet or moon.
Green, purple, red, black, and brown colored.
The color is often determined by the amount of iron, and organic material present in the rock.
Schist: It has crystals
can be light or dark colored.
Marble: Can be identified by its smooth glassy texture.
Very hard rock.
Mostly composed from sandstone.
- Lightweight: The weight is about 1/3 of a stone.
- Low noise: Take a piece of amber and knock it careful against your teeth. I sounds hollow.
- Warmth: Stone feels colder than amber. ...
- Fire test: Amber burns with a reddish, sooty flame. ...
- Softness: If you scratch amber with a knife so you get small slivers.
Generally light coloured, grey through yellow.
Smooth to rough to touch,
Dependent on composition and or mode of formation.
- Coal is made largely of carbon but also features other elements such as hydrogen,oxygen, sulfur and nitrogen.
- Coal starts off as plant matter at the bottom of water. It is eventually covered and deeply buried by sediments where over time metamorphosis (a change in form) takes place.
- Different types of coal contain different amounts of carbon. Lignite contains only around 60 to 75%, while anthracite contains more than 92%.
- Anthracite is a hard, shiny, black coal that burns with a blue, smokeless flame. While most forms of coal are associated with sedimentary rock, anthracite undergoes metamorphism and is linked to metamorphic rocks.
- Coal has long been burned to create electricity and heat. The use of coal is increasing every year, in 2006 the world consumed over 6,000,000,000,000 kilograms of coal!
- Coal is the world’s largest source of energy for the production of electricity.
Gypsum is a soft sulfate mineral composed of calcium sulfate dihydrate, with the chemical formula CaSO. 2H2O. It can be used as a fertilizer, is the main constituent in many forms of plaster and is widely mined.
Shale is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin laminae or parallel layering or bedding less than one centimeter in thickness, called fissility.Mudstones, on the other hand, are similar in composition but do not show the fissility.