Search the Dictionary

To vary by turns; as, the land alternates between rocky hills and sandy plains.

the decomposition of which leads to the formation of alum, which often effloresces on the rock.

An extensive group of fossil cephalopods often very abundant in Mesozoic rocks. See Ammonite.

ging firearms and ordnance of all kinds; as powder, balls, shot, shells, percussion caps, rockets, etc.

as a general term for the whole species). Amphibole is a constituent of many crystalline rocks, as syenite, diorite, most varieties of trachyte, etc. See Hornblende.

A variety of trap or basaltic rock, containing small cavities, occupied, wholly or in part, by nodules or geodes of different minerals, esp. agates, quartz, calcite, and the zeolites. When the imbedded minerals are detached or removed by decomposition, it is porous, like lava.

Pertaining to, or having the nature of, the rock amygdaloid.

An eruptive rock allied to trachyte, consisting essentially of a triclinic feldspar, with pyroxene, hornblende, or hypersthene.

owering plants of northern climates, of which the original species was found growing on a rock surrounded by water.

r family, commonly occurring in small glassy crystals, also a constituent of some igneous rocks. It is a lime feldspar. See Feldspar.

A granular igneous rock composed almost exclusively of a soda- lime feldspar, usually labradorite.

A structure of bedded rocks in which the beds on both sides of an axis or axial plane dip away from the axis; an anticlinal.

d, occupying the space between the crystalline lens and the cornea. (See Eye.) -- Aqueous rocks (Geol.), those which are deposited from water and lie in strata, as opposed to volcanic rocks, which are of igneous origin; -- called also sedimentary rocks.

btained from several species of lichen (Roccella tinctoria, etc.), which grow on maritime rocks in the Canary and Cape Verd Islands, etc. Tomlinson.

An extinct genus of Bryzoa characteristic of the subcarboniferous rocks. Its form is that of a screw.

An ancient wormhole in sand, preserved in the rocks. Dana.

absinthium, or common wormwood, is well known, and A. tridentata is the sage brush of the Rocky Mountain region.

nt. Artificial asphalt is prepared from coal tar, lime, sand, etc. Asphalt stone, Asphalt rock, a limestone found impregnated with asphalt.

Rubbish or refuse consisting of broken rock containing little or no ore. Weale.

An instrument for boring or perforating soils or rocks, for determining the quality of soils, or the nature of the rocks or strata upon which they lie, and for obtaining water. Auger bit, a bit with a cutting edge or blade like that of an anger.