ChertChert ('tʃɜrt) is a hard, fine-grained sedimentary rock composed of microcrystalline or cryptocrystalline quartz, the mineral form of silicon dioxide (SiO2). Chert is characteristically of biological origin, but may also occur inorganically as a chemical precipitate or a diagenetic replacement, as in petrified wood. Chert is typically composed of the petrified remains of siliceous ooze, the biogenic sediment that covers large areas of the deep ocean floor, and which contains the silicon skeletal remains of diatoms, silicoflagellates, and radiolarians.
AsbestosAsbestos (æsˈbɛstəs,æzˈ-,-tɒs ) is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre (particulate with length substantially greater than width) being composed of many microscopic "fibrils" that can be released into the atmosphere by abrasion and other processes. Inhalation of asbestos fibres can lead to various dangerous lung conditions, including mesothelioma, asbestosis, and lung cancer.
Volcanic ashVolcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to refer to all explosive eruption products (correctly referred to as tephra), including particles larger than 2 mm. Volcanic ash is formed during explosive volcanic eruptions when dissolved gases in magma expand and escape violently into the atmosphere.
Silicon dioxideSilicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , most commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and most abundant families of materials, existing as a compound of several minerals and as a synthetic product. Notable examples include fused quartz, fumed silica, silica gel, opal and aerogels. It is used in structural materials, microelectronics (as an electrical insulator), and as components in the food and pharmaceutical industries.
TridymiteInfobox mineral | name = Tridymite | category = Oxide mineral (or tectosilicate), quartz group | boxwidth = | boxbgcolor = | image = Tridymite tabulars - Ochtendung, Eifel, Germany.jpg | imagesize = 260px | caption = tabular tridymite crystals from Ochtendung, Eifel, Germany | formula = SiO2 | molweight = 60.08 g/mol | strunz = 4.DA.10 | IMAsymbol = Trd | system = Orthorhombic (α-tridymite) | class = Disphenoidal (222) H–M symbol: (222) | symmetry = C2221 | color = Colorless, white | habit = Platy – sheet forms | cleavage = {0001} indistinct, {1010} imperfect | fracture = Brittle – conchoidal | mohs = 7 | luster = Vitreous | refractive = 'nα=1.
