Geology or Related Geological Terms +
(a glossary, or dictionary, of terms used in geology; the science of the earth including its origin, composition, structure, and history)
2. A hard, dense, shiny variety of coal, containing over 90 percent carbon and a low percentage of ash and impurities, which causes it to burn without flame, smoke, or odor.
Because of its purity, anthracite gives off relatively little sulfur dioxide when burned.
2. An upfold of layered rocks in an archlike structure.
A semiprecious gemstone which is used in jewelry.
2. A group of islands, or an area of sea containing a group of islands.
The islands of an archipelago are usually volcanic in origin, and they sometimes represent the tops of peaks in areas around continental margins flooded by the sea.
The Aegean Sea being full of island chains, the meaning was extended in Italian to "any sea studded with islands".
The Aegean archipelago lies between Greece and Turkey.
Commercial asbestos is generally either made from serpentine ("white" asbestos) or from sodium iron silicate ("blue" asbestos).
The fibers are woven together or bound by an inert material. Over time the fibers can work loose and, because they are small enough to float freely in the air or be inhaled, asbestos usage is now strictly controlled, exposure to its dust can cause cancer.
Asphalt is mixed with rock chips to form paving material, and the purer varieties are used for insulating material and for waterproofing masonry. It can be produced artificially by the distillation of petroleum.
The asthenosphere is a region in the upper mantle of the earth's interior, characterized by low-density, semiplastic (or partially molten) rock material chemically similar to the overlying lithosphere.
The upper part of the asthenosphere is believed to be the zone upon which the great rigid and brittle lithospheric plates of the earth's crust move around.
The asthenosphere is generally located between 45–155 miles (72–250 km) beneath the earth's surface, though under the oceans it is usually much nearer the surface and at mid-ocean ridges rises to within a few miles or kilometers of the ocean floor.
It is a most common mineral and one of the most common minerals on the face of the earth, consisting of about four percent by weight of the earth's crust and is formed in many different geological environments.
It is used in cements and mortars, in the production of lime, and limestone is used in the steel industry; in the glass industry, as ornamental stone, in chemical and optical uses, and as mineral specimens.
A lack of cleavage also increases its durability. Its crystals are barrel-shaped prisms of the trigonal system.
2. The second hardest natural mineral known to science.Its two varieties are sure to be on any list of gemstones. The red variety of corundum is known as ruby and all the other colors of corundum are known as sapphire.
Besides being used as gemstones, it is also utilized as an abrasive.
It is well known that diamond is the hardest substance found in nature, but few people realize that diamond is four times harder than the next hardest natural mineral, corundum (sapphire and ruby).
Diamond is usually utilized as a gemstone and an abrasive, as well as in scientific uses.
Index of additional Scientific and Technological Topics.
