mica Min.
(ˈmaɪkə)
[a. L. mīca grain, crumb.
The mod.L. use in Mineralogy was prob. originally contextual; the development of the specialized meaning may have been due to erroneous association with micāre to shine.]
† 1. A small plate of talc, selenite, or other glistening crystalline substance found in the structure of a rock. In pl. micæ. Obs.
| 1706 Phillips (ed. Kersey), Mica,..Glimmer, or Cat-silver; a Mettallick Body like Silver, which shines in Marble, and other Stones, but cannot be separated from them. a 1728 Woodward Nat. Hist. Fossils (1729) I. i. viii. 170 A pale brown Earth, with very small Micæ in it. 1748 J. Hill Hist. Fossils 556 Dr. Woodward imagin'd the white parts of this as of the other Micæ in general to be Spar. 1803 Sarrett New Pict. Lond. 114 A great variety of Micæ or spangle stones. |
2. Any one of a group of similar minerals composed essentially of silicate of aluminium variously combined with the silicates of other bases, such as soda, potash and magnesia, and occurring either in minute glittering plates or scales in granite and other rocks, or in crystals characterized by their perfect basal cleavage and their consequent separability into thin, transparent and usually flexible laminæ.
water mica, a trade name for clear, colourless mica.
| 1778 Woulfe in Phil. Trans. LXIX. 29 Mica or Glimmer. This..is composed of very thin flexible flakes, more or less large. 1835 R. D. & T. Thomson's Rec. Gen. Sci. II. 445 Pinchbeck mica, iron pyrites, and titaniate of iron occur as accidental constituents. 1860 Tyndall Glac. 3 Mica is a crystal which cleaves very readily in one direction. 1903 Edin. Rev. Oct. 390 A film of mica. 1905 Jrnl. Franklin Inst. Sept. 200 The clear kind is known to the trade as ‘water mica’. |
3. attrib. and
Comb., as
mica battery,
mica goggles,
mica insulation,
mica plate;
mica-packed,
mica-scaled,
mica-topped adjs.;
mica flap, the flap of a mica valve;
mica-powder, a form of dynamite in which the siliceous earth is replaced by mica in fine scales;
mica-schist,
-slate, a slaty metamorphic rock composed of quartz and mica;
mica valve, a device consisting of a flap of mica hinged at the top which is used to allow air to flow in one direction only.
| 1849 Noad Electricity (ed. 3) 148 The lacquered knob of the *mica battery. |
| 1906 J. W. Thomas Ventilation, Heating & Lighting of Dwellings ii. 27 There are many chimney ventilators on the market, some having *mica flaps..to shut against a down current. 1934 E. L. Joselin Ventilation iii. 44 Outlets with mica flaps are frequently fitted into chimney breasts near the ceiling. 1964 J. S. Scott Dict. Building 207 Mica-flap valve. |
| 1905 Daily Chron. 10 Aug. 5/6 A polo cap, *mica goggles,..and the usual..allowance of lard constituted Burgess's costume. |
| 1897 Daily News 20 July 6/2 It fused the *mica insulation of wires. |
| 1909 Westm. Gaz. 9 Mar. 4/3 A new three-point sparking-plug..which has no asbestos or *mica-packed joints. a 1963 S. Plath Crossing Water (1971) 44, I shone, mica-scaled, and unfolded To pour myself out like a fluid. |
| 1837 Brewster Magnet. 312 The successive thicknesses of the *mica plates. |
| 1881 Raymond Mining Gloss., *Mica-powder. |
| 1833 Lyell Princ. Geol. III. 237 The sterile *mica-schist is barely covered with vegetation. 1878 Lawrence tr. Cotta's Rocks Class. 234 A complete series of transitions from..gneiss through mica-schist into clay-slate. |
| 1819 Bakewell Introd. Mineral. 477 *Mica-slate, or micaceous schistus. 1877 Raymond Statist. Mines & Mining 229 A large number of fine lodes, all occurring in limestone and mica-slate. |
| 1958 A. Wilson Middle Age of Mrs Eliot iii. 381 David banged his fist on the *mica-topped table in front of him so that its little contemporary steel-tube legs rattled. |
| 1880 S. S. Hellyer Plumber & Sanitary Houses (ed. 2) xxii. 262 When no convenient place can be found for leaving the mouth of the induct-pipe open to the atmosphere, a *mica-valve can be fixed over it. 1909 G. B. Shaw in Trans. Medico-Legal Soc. VI. 217 One day on the Health Committee a question came up with regard to a mica valve not being in order. |