serpentine

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serpentine , hydrous silicate of magnesium. It occurs in crystalline form only as a pseudomorph having the form of some other mineral and is generally found in the form of chrysotile (silky fibers) and antigorite and lizardite (which are both tabular). Chrysotile is also known as commercial asbestos which has been used for fireproofing and insulating material. It is commonly some shade of green, but may also be reddish, yellowish, black, or nearly white. It has a greasy or silky luster and is often translucent, even in large masses. Serpentine can be found in igneous rock, but it is more often a secondary mineral, usually resulting from the alteration of minerals or rocks containing magnesium, and it occurs very widely throughout the world, mainly as a product of metamorphism in rocks rich in olivine, pyroxene and amphibole. Serpentine rocks and basalts in the central zone of the Appalachian Mts of the eastern United States represent sutures of old oceanic crust, known as ophiolites, crushed between colliding continents. Essentially all lower crust and upper mantle rocks recovered from the mid-ocean ridges have been serpentinized to some degree by reaction with seawater. Serpentine rocks are classified as common serpentine and precious serpentine, the common serpentine being darker, less translucent, and sometimes impure. Serpentine is sometimes used as a gem and the massive varieties are quarried. Used like marble for decorative purposes, when serpentine is mixed with calcite, dolomite, or magnesite, a mottled or veined rock called verd antique is produced, although the masses are frequently jointed and only small slabs can be secured. Serpentine takes a beautiful high polish, but it is easily cracked and discolored by exposure to the weather and is consequently of little value for exterior use. Serpentine deposits are found in Canada, S Africa, and Vermont and Arizona in the United States.

serpentine A group of minerals belonging to the 1:1 group of phyllosilicates (sheet silicates) with the composition Mg₆ [Si₄O₁₀](OH)₈ and including the minerals chrysotile (the asbestiform variety), lizardite, and antigorite; sp. gr. 2.55–2.60; *hardness 2.0–3.5; monoclinic; chrysotile is fibrous whereas lizardite and antigorite occur as flat tabular crystals or massive; various shades of green, also brown, greywhite, or yellow; greasy to waxy lustre, occasionally silky; formed from altered olivine and orthopyroxene. It results from the alteration of ultramafic (see ULTRABASIC) rocks either by hydrothermal action at a late stage or by alteration during metamorphism, chrysotile forming first and then altering to antigorite; it is a constituent of ophicalcites, a serpentine-calcite rock derived from the dedolomitization (see DEDOLOMITE) of a siliceous dolomite. It is used extensively as a facing stone and for ornament; chrysotile has been used as a source of commercial asbestos in Thetford, Canada. Lizardite occurs on the Lizard Peninsula, Cornwall, UK.

ser·pen·tine / ˈsərpənˌtēn; -ˌtīn/ • adj. of or like a serpent or snake: serpentine coils. ∎  winding and twisting like a snake: serpentine country lanes. ∎  complex, cunning, or treacherous: his charm was too subtle and serpentine for me. • n. 1. a dark green mineral consisting of hydrated magnesium silicate, sometimes mottled or spotted like a snake's skin. 2. a thing in the shape of a winding curve or line, in particular: ∎  a riding exercise consisting of a series of half-circles made alternately to right and left. 3. hist. a kind of cannon, used esp. in the 15th and 16th centuries. • v. [intr.] move or lie in a winding path or line: fresh tire tracks serpentined back toward the hopper.

serpentine, a small ship's handgun of the 15th and 16th centuries. It had a calibre of 3.8 centimetres (1.5 in.) and fired a 156 gram (5.5 oz) shot with a charge of the same weight of ‘cannon corn’ powder. The maximum, or random, range was 1,300 paces. When the powder used was ‘fine corn’, the same quality as used in muskets, the charge was reduced by one-quarter. Serpentines were upper-deck or ‘castle’ guns, i.e. fired into the waist of an enemy ship from a ship's forecastle or after castle, and were used purely in an anti-personnel role. See also robinet.

serpentine Group of sheet silicate minerals, hydrated magnesium silicate (Mg₃Si₂O₅(OH)₄). Serpentine minerals come in various colours, usually green, although sometimes brownish, with a pattern of green mottling. They have monoclinic system crystals. They are commonly used in decorative carving; fibrous varieties are used in asbestos cloth. Hardness 2.5–4; r.d. 2.5–2.6.

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