Glossary of Stone and Masonry Terms

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Agglomerate - A man-made product fabricated to look like quarried stone. Usually composed of stone chips or fragments embedded in a matrix of mortar or thermosetting resins.

Alabaster - A mane given to a stalagmitic or stalactitic calcium carbonate and a calcium sulfate (gypsum). The calcium carbonate variety is a translucent stone of yellowish milky color, while the calcium sulfate has a fine granular quality. The latter was abundant in Tuscany and Piedmont, and when carved into statues and vases is frequently sold a “Florentine Marble”.

Alumina - Aluminum oxide (Al2O3)

Anhydrite - A specific calcined gypsum rock whose chemical composition is anhydrous calcium sulfate (CaSO4). It is used in Portland Cement to control set.

Anhydrous - a hydrate which has given up all of its previously held water molecules.

Aragonite - a translucent white mineral found in calcium carbonate.

Argillaceous - Clay-bearing rock.

Arris - The edge of an external angle formed by the intersection of two surfaces.

Artificial Marble - Man-made marble. See Agglomerate.

Ashlar - Accurately shaped, rectangular-cut stone unit also referred to as “cut stone”.


Basalt - A fine-grained, dense, igneous rock, but unlike granites contains little or no quartz or feldspars. The colors of basalts are very dark green to black and often sold as granites.

Bed Joint - A horizontal layer of mortar on which building units are laid.

Biotite - A dark, iron and magnesium-rich mica found in granite.

Bluestone - A blue to bluish-green argillaceous metamorphic sandstone of even texture and bedding, historically quarried neat the Hudson River.

Breccia - A name applied to both granite and conglomerate stone because of the coarse and angular particles present.

Brick - A man-made solid or hollow building unit which is made from clay or shale.

Brownstone - A dark-brown or reddish-brown sandstone. A sedimentary rock.

Bullnose - A rounded outside corner or edge.

Butt Joint - An external corner formed with the meeting of two square-edged stones, either one overlapping the other.


Calcareous - Calcium-bearing rock.

Calcine - The removal of water molecules in hydrates by heat.

Calcite - The natural mineral form of calcium carbonate (CaCO3).

Calcite Marble - A crystalline variety of marble or limestone containing not more than 5% magnesium carbonate.

Calcium Oxide - Calcined limestone (CaO).

Carbonate - A salt of carbonic acid.

Carbonic Acid - A weak acid (H2CO3).

Cast Stone - A man-made stone. See Agglomerate.

Caulking - The application of a sealant in a joint or opening to prevent the passage of water, air, dust and noise.

Cement - A hydraulic mixture, without aggregate, consisting of a calcined mixture of clay and pulverized limestone.

Concrete - A composite material consisting of Portland Cement, aggregate, and water: when mixed together, will result in a chemical action that will set and harden into a rock-like mass.

Conglomerate - A stone similar to sandstone but the rock particles are rounded or angular gravel rather than sand.

Coping - A cap or covering course on top of a masonry wall. Designed to shed water, protect the top, and provide a finished, closed appearance to the wall.

Course - A continuous layer of building units running horizontally in a wall.

Cut Stone - See Ashlar


Dimensional Stone - Natural building stone that has been selected, trimmed or cut to specific shapes and/or sizes.

Dolomite - a calcium magnesium carbonate [CaMg(CO3)2]Dolomite Marble - A crystalline variety of marble or limestone containing more than 40% magnesium carbonate.

Draft - The tooled strip or border of a faced stone, also known as a margin.

Drip - A slot cut into the bottom of a projected stone to interrupt the capillary action of water.


Efflorescence - A white powdery deposit of soluble salts of calcium, potassium, and sodium which forms on the surfaces of masonry. Efflorescence is caused by the release of excess “water of crystallization” and/or moisture penetration, thereby, causing the leaching of these salts to the surface when the water evaporates.
See article "Efflorescence, Causes, Removal and Prevention"


Face - The exposed surface of a stone with its specified finish.

Feldspar - Any of a group of crystalline minerals, all silicates of aluminum with either potassium, sodium, calcium, or barium. An essential constituent of nearly all crystalline rocks.

Fieldstone - An uncut, well-rounded stone found on the surface or in the soil of the earth.

Flagstone - A stone used for outdoor paving, fabricated from natural thin rock, or split from rock which cleaves easily.

Fleuri Cut - Unique to the marble industry, it is a cut parallel to the natural bedding plane, See Vein Cut.

Foliation - The layered or banded structure of rock in which the mineral grains became re-aligned at right angles to a directional force that existed during metamorphism.

Full Bed Mortar - The troweling of both the setting bed mortar and pointing mortar in one operation. See. Setting Bed and Pointing.


Gneiss - A metamorphic rock with a banded or coarsely foliated structure; often called “Trade Granite”.

Granite - An unstratified igneous rock composed of coarse grains or crystals of quartz, feldspar, mica and sometimes hornblende.

Gravel - Composed chiefly of quartz but may contain granite, limestone, basalt and other rocks.

Grout - Mortar with a high water ratio used to fill open joints between installed stone or building units. Normally, grout is worked into these joints with a hard rubber float.

Gypsum - A hydrated calcium sulfate (CaSO42H20). It is formed naturally as the result of the reaction of sulfuric acid produced by the decomposition of pyrite upon the calcium carbonate of shells existing in clay. A sedimentary rock.


Halite - Rock salt; Sodium chloride (NaCl). A sedimentary rock.

Hemihydrate - A hydrate which contains one-half of a molecule of water compared to one molecule of the principal element or compound forming the hydrate.

Hornblende - A group of minerals including calcium, iron, magnesium, and aluminum silicates.

Hydrate - A mineral formed by the combination of water and some other elements or compounds.

Hydrous - Containing chemically combined water.


Igneous Rock - One of the three principal groups of rock that make up the earth’s surface; formed by the solidification of molten matter. See Sedimentary Rock and Metamorphic Rock>


Kaolinite - A hydrous aluminum silicate mineral.


Limestone - A sedimentary rock composed predominantly of calcium carbonate. Limestone was formed by the decomposition of rock, soil, plant and animal life that was deposited at the bottom of lakes or seas. Any limestone may be called a marble if it is capable of taking a polish.


Marble - A metamorphic limestone in a more or less crystalline or crystalline-granular state. Any limestone capable of taking a polish can also be called a marble.

Margin - See Draft.

Masonry - A built-up combination or construction of building units or materials of clay, shale, concrete, glass, gypsum, stone or other similar products bonded together with mortar.

Metamorphic Rock - One of the three classes of rock making up the earth’s surface; formed from igneous and sedimentary rocks that were changed by heat, pressure, and hydrothermal solutions. See igneous Rock and Sedimentary Rock.

Mica - Any of a group of mineral silicates in a muti-layered form.

Mortar - A plastic mixture of cement, water, and fine aggregates which combine together through a chemical process of crystallization to form a hardened solid that bonds building units together. See Water of Crystallization.

Mortar Bed - A troweled layer of mortar, in a plastic state, in which building units will be set.

Muscovite - A white, aluminum-rich mica found in granite.


Natural Bed - The horizontal stratification of rock as it was formed in the earth.


Onyx - A variety of quartz in crystalline form of calcium carbonate. It is characterized by a structure of parallel bands each differing in color or in the degree of translucency. Considered to be a marble because it can take a polish.

Oolitic Limestone - A limestone formed in the sea, consisting of spherical or sub-spherical particles of calcite-coated grains of sand.


Paver - A block or chunk of stone or brick used for paving.

Plaster of Paris - a calcined gypsum in a hemihydrate state (CaSO41/2H2O).

Pointing - the troweling of mortar into a building unit joint after the setting bed mortar has hardened. See Full Bed Mortar and Setting Bed Mortar.

Portland Cement - A hydraulic cement product obtained by pulverizing and calcining a properly proportioned mixture of three minerals - lime, silica, and alumina.

Pyrite - The natural sulfides of certain metals. The most common is iron pyrite, which is iron disulfide (FeS2), a brittle mineral that is a brassy yellow in color with greenish-black streaks.


Quarry - The location of a mining operation where a natural deposit of rock is extracted from the earth as stone through an open pit or an underground mine.

Quartz - Silicon dioxide (Si02) occurring in hexagonal crystal form.

Quartzite - A metamorphic rock consisting largely or entirely of quartz. Most quartzites are formed from sandstone.

Quartzitic Sandstone - A metamorphic sandstone consisting of quartz grains cemented with silica, but not as hard as quartzite. Geologically, it is an intermediate rock between sandstone and quartzite.

Quicklime - Calcium oxide which is a crushed limestone that has been calcined.

Quirk Joint - An external corner formed with the meeting of two stone units each with an identical, mirror-imaged, combination of a square and mitered edge. The joint is formed along the mitered portion.

Quoins - Blocks of stone forming external corners of masonry walls.


Reglet - A marrow, flat recess to receive and secure flashing.

Rubble - Rough, irregular-shaped stone.

Rusticated - Emphasized joints, recessed or beveled, which are cut or formed in stonework.


Schist - Any metamorphic crystalline rock having a foliated structure. It can easily be split into slabs or sheets.

Sealant - A material used to fill and seal a joint or opening. See Caulking.

Sedimentary Rock - One of three classes of rock which make up the earth’s outer crust; formed from the disintegration of older rocks, soils, plants, and animals. See Igneous rock and Metamorphic rock.

Serpentine - A hydrous magnesium silicate (H4Mg3Si2O9). Usually green, lustrous, and translucent, but could also be red, yellow, black or white. Serpentine stone takes a high polish but can crack or discolor easily.

Setting Bed Mortar - The troweling of mortar to set building units, but withe the exposed joint raked out for the application of the pointing mortar or grout to be done later. See Full Bed Mortar, Pointing, and Grout.

Siliceous - Silica-bearing rock.

Slate - A fine-grained metamorphic rock derived form clays and shales.

Staining - A phenomenon of discoloration on newly installed limestone. Buff limestone will exhibit a brown stain while gray limestone will exhibit a dark gray stain. This staining is similar to efflorescence but it is the organic matter in the stone which is leaching out through the release of excess water of crystallization of the setting mortar.


Thick Bed Mortar - A mortar setting bed over 1/2" and up to 4" thick. The minimum required “thickbed thickness” is a function of application usage, installed material, and the supporting substrate. See Setting Bed Mortar.

Thin Bed Mortar - A mortar setting bed up to 1/2" thick. See Setting Bed Mortar.

Trade Granite - See Gneiss.

Travertine - A calcium carbonate rock having a coarsely cellular structure formed form the deposits of spring and cave waters. Travertine stone can be called either a marble or limestone.


Vein Cut - Unique to the marble industry, it is a cut perpendicular to the natural bedding plane. See Fleuri Cut.

Veneer - An outside, non-load bearing wythe of masonry used as a facing material.

Verde Antique - A dark green serpentine marble or granite marked with white veins of calcite


Water of crystallization - The extra water required to assist in the crystallization process when forming a hydrate (mortar, cement, concrete, plaster, etc.). When the hydrate gives up this excess water, at ambient temperatures, the result is a surface deposit known as efflorescence or staining.

Water Table - A continuous course of building units on the outside wall, near the ground, with a horizontal projection or ledge. It is often shaped with a slope and a drip to limit the amount of water passing over the wall or surface below.

Weep Hole - A small opening in a masonry cavity wall through which accumulated water or condensation can drain to the exterior.

Window Sill - The bottom section of a window frame and/or the bottom section of an exterior masonry window opening.

Window Stool - A narrow shelf fitted across the lower part on the inside of a window opening.