Browse Items (13 total)

Plaster of Paris is exactly that - a plaster that, originally, came from Paris, France. It is made by calcining the mineral gypsum, CaSO4.2H2O, at about 180°C, driving off water to give the anhydrite 2CaSO4.H2O. When mixed with water it rehydrates…

Calcium carbonate is a common substance found in things like shells, rocks, pearls, and shells. Its most common natural forms are chalk, limestone, and marble, produced by the sedimentation of the shells of small fossilized snails, shellfish, and…

Soda lime glass is the glass of windows, bottles and light bulbs, used in vast quantities, the commonest of them all. The name suggests its composition - 13-17% NaO (the "soda"), 5-10% CaO (the "lime") and 70-75% SiO2 (the "glass"). It has a low…

Slates are formed by the deposition of clay and mud, consolidated by pressure. Their most striking features are their ability to be cleaved, producing flat slabs or sheets, and their impermeability to water in a direction normal to the cleavage…

Silicon is the second most abundant element, exceeded only by oxygen and making up 26% of the earth's crust by weight. It is found largely as silicon oxides such as sand (silica), quartz, rock crystal, amethyst, agate, flint, jasper and opal, and as…

Silicon carbide (SiC, carborundum), made by fusing sand and coke at 2200 C, is the grit on high quality sandpaper. It is very hard and maintains its strength to 1400C high temperature, has good thermal shock resistance, excellent abrasion…

Alumina (Al2O3) is to technical ceramics what mild steel is to metals - cheap, easy to process, the workhorse of the industry. It is the material of spark plugs, electrical insulators and ceramic substrates for microcircuits. In single-crystal form…

Borosilicate glass is soda-lime glass with most of the lime replaced by borax, B203. It has a higher melting point than soda-lime glass and is harder to work, but it has a lower expansion coefficient and a high resistance to thermal shock, so it is…

Granite is one of the most durable of materials. The pyramid of Giza (2980 BC) was built of limestone cased in granite. It is a coarse-grained igneous rock, very hard and compact. It takes a fine polish, showing the beauty of its crystals. It is the…

Graphite, archaically referred to as plumbago, is a crystalline form of carbon, a semimetal, a native element mineral, and one of the allotropes of carbon. Graphite is the most stable form of carbon under standard conditions. Therefore, it is used in…