(2) In stratified rocks the unit layer formed by semidentation of variable thickness, and commonly tilted or distorted by subsequent deformation generally develops a rock cleavage, parting, or jointing along the planes of stratification. Sometimes applied also to the surface of parting between sheets. (1) In granites and marbles, a layer or sheet of the rock mass that is horizontal, commonly curved and lenticular as developed by fractures. bed – the top or bottom of a joint, natural bed surface of stone parallel to its stratification.basalt – a dense-textured (aphanitic), igneous rock relatively high in iron and magnesia minerals and relatively low in silica, generally dark grey to black, and feldspathic a general term in contradistinction to felsite, a light-colored feldspathic and highly siliceous rock of similar texture and origin.

banker – bench of timber or stone on which stone is shaped.

balustrade – an ornamental fencing consisting of a series of balusters supporting a handrail or molding.

baluster – a miniature pillar or column supporting a rail, used in balustrades.

back arch – a concealed arch carrying the backing of a wall where the exterior facing is carried by a lintel.

ashlar – stones basically rectangular in shape and exhibiting the split face of the stone revealing striations that can be quite colorful.

arris – a natural or applied line on the stone from which all leveling and plumbing is measured.

Also called arkosic sandstone, feldspathic sandstone.

arkose – a sandstone containing 10% or more clastic grains of feldspar.

argillite – a compact sedimentary rock composed mainly of clay and aluminum silicate minerals.

architrave – the member of an entablature resting on the capitals of columns and supporting the frieze.

arch – a curved stone structure resting on supports at both extremities used to sustain weight, to bridge or roof an open space.

apex stone – uppermost stone in a gable, pediment, vault or dome.

anchors – types of stonework include those made of flat stock (strap, cramps, dovetails, dowel, strap and dowel, and two-way anchors) and round stock (rod cramp, rod anchor, eyebolt and dowel, flat-hood wall tie and dowel, dowel and wire toggle bolts).

agate – a variegated variety of quartz showing colored bands or other markings (clouded, mosslike, etc.).

adhered – veneer secured and supported through adhesion to an approved bonding material applied over an approved backing.

abutment – a solid stone “springer” at the lowest point of an arch or vault.

abrasive finish – a flat non-reflective surface finish for marble.

Sheet vs plate thickness