premise: the siliceous <mask> about geysers; alluvial <mask>s; marine <mask>s.
hypothesis: the best context for <mask> here is A frame or ring of wire or hard paper fitting into the cartridge case used in some shotguns, and holding the shot together when discharged, to secure close shooting; also, a device for slightly narrowing the bore at the muzzle for the same purpose.; but not Mineral deposits and rock masses designated with reference to their origin.