Alum slate

Slate Slate (sl[=a]t), n. [OE. slat, sclat, OF. esclat a shiver, splinter, F. ['e]clat, fr. OF. esclater to shiver, to chip, F. ['e]clater, fr. OHG. sleizen to tear, slit, split, fr. sl[=i]zan to slit, G. schleissen. See {Slit}, v. t., and cf. {Eclat}.] 1. (Min.) An argillaceous rock which readily splits into thin plates; argillite; argillaceous schist. [1913 Webster]

2. Any rock or stone having a slaty structure. [1913 Webster]

3. A prepared piece of such stone. Especially: (a) A thin, flat piece, for roofing or covering houses, etc. (b) A tablet for writing upon. [1913 Webster]

4. An artificial material, resembling slate, and used for the above purposes. [1913 Webster]

5. A thin plate of any material; a flake. [Obs.] [1913 Webster]

6. (Politics) A list of candidates, prepared for nomination or for election; a list of candidates, or a programme of action, devised beforehand. [Cant, U.S.] --Bartlett. [1913 Webster]

{Adhesive slate} (Min.), a kind of slate of a greenish gray color, which absorbs water rapidly, and adheres to the tongue; whence the name.

{Aluminous slate}, or {Alum slate} (Min.), a kind of slate containing sulphate of alumina, -- used in the manufacture of alum.

{Bituminous slate} (Min.), a soft species of sectile clay slate, impregnated with bitumen.

{Hornblende slate} (Min.), a slaty rock, consisting essentially of hornblende and feldspar, useful for flagging on account of its toughness.

{Slate ax} or {Slate axe}, a mattock with an ax end, used in shaping slates for roofs, and making holes in them for the nails.

{Slate clay} (Geol.), an indurated clay, forming one of the alternating beds of the coal measures, consisting of an infusible compound of alumina and silica, and often used for making fire bricks. --Tomlinson.

{Slate globe}, a globe the surface of which is made of an artificial slatelike material.

{Slate pencil}, a pencil of slate, or of soapstone, used for writing on a slate.

{Slate rocks} (Min.), rocks which split into thin lamin[ae], not necessarily parallel to the stratification; foliated rocks.

{Slate spar} (Min.), a variety of calcite of silvery white luster and of a slaty structure.

{Transparent slate}, a plate of translucent material, as ground glass, upon which a copy of a picture, placed beneath it, can be made by tracing. [1913 Webster]