Natural Stone Definitions



In stone carving, to cut away material, leaving parts in relief.

Abrasive Finish

A non-reflective surface finish. An abrasive finish may be defined by the grit size of the abrasive.

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Abrasive Hardness

A measure of the wearing performance of stone for floors, stair treads, and other areas subjected to abrasion by foot traffic


The amount of water absorbed by a stone, expressed as a percentage by weight.


A solid stone springer at the lowest point of an arch or vault.


In masonry, any ingredient added to mortar or concrete to speed the curing process.

Acid Wash Finish

Acids can be used to clean the surface of the stone or to change its appearance, depending on the type of acid and the length of its application. Acid wash is an alternative way to achieve an antiqued look. It can also produce similar results to waterjet finishing.

Most significantly, an acid wash can be applied retroactively, meaning you can change the look of already installed stone. Surface Roughness can vary from slick (< 1/64”) to somewhat rough (1/16-1/4”) depending on the process. Acid washes can be applied by hand or automated machine.

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Used in reference to stone veneer, secured and supported by adhesion of an approved bonding material over an approved backing.


A material other than water, aggregates, lime or cement, added to concrete or mortar at the time of mixing. Admixtures are typically added to function as water repellents, coloring agents or to adjust the curing rate of the concrete or mortar.


A volcanic, quartz-based stone containing a variety of colored aggregates and pumice in a quartz matrix. Quarried in Mexico.

Adze Finish

Crushing blows done with old fashioned hand tools create a stark, Stone Age, pleasing contrast to the natural color of a stone face. Adze patterns are generally random. Often used on a split-faced wall surface, adze finishes highlight lintels, sills, and copings. Adze finishes can be used to create various looks, including modern, linear, and rustic.

Honing an adze surface can darken it further to create a stunning surface. Frost flower is a variation of the adze finish. Surface roughness can vary the texture from slick (< 1/64”) to very rough (>2”) depending on the process. Adze finishes can also be produced by a machine, although hand-made adze is generally considered more attractive.

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A variegated, translucent, cryptocrystalline variety of quartz showing colored bands or other markings (clouded, moss-like, etc.).

Agglomerated Stone

A man-made product composed of crushed stone combined with resin. See also Engineered Stone and Cultured Stone.


A small mass of rock, having occurred naturally (as in sand or gravel) or by means of manufacture (as in a crushed aggregate product), used either in a loose, noncohesive state or as an ingredient in mortar or concrete products.


A fine-grained and translucent variety of gypsum, generally white in color. Commonly used in decorative applications as it can be cut and carved easily with a knife or saw. Term is often incorrectly applied to fine-grained marble.


Pertains to a highly basic, as opposed to acidic, substance. For example, hydrogen or carbonate of sodium or potassium.

Allowable Capacity

The safe load that can be resisted by a stone anchor, determined by dividing the ultimate capacity by the factor of safety.

Ambient Temperature

Temperature of the surrounding environment.


A corrosion-resistant metal fastener used for securing dimensional stone to a structure or adjacent stone units. Anchor types for stonework include those made of flat stock (straps, dovetails) and round stock (rod cramp, rod anchor, eyebolt, and dowel).


The means by which slabs are secured to a self-supporting structure.

Angle of Repose

The angle of repose, or critical angle of repose, of a granular material is the steepest angle of descent or dip relative to the horizontal plane to which a material can be piled without slumping. At this angle, the material on the slope face is on the verge of sliding. The angle of repose can range from 0° to 90°.


Having properties, either visual or mechanical, that differ based on the direction in which they are measured. All stones are anisotropic to some degree, but the sedimentary stones typically have the greatest degree of anisotropy.


A dark-colored igneous rock consisting mostly or entirely of calcic plagioclase.


American National Standards Institute

Antiqued Finish

Antiqued stone is tumbled with sand and pebbles to create a weathered, aged finish. The process also stimulates the stone’s additional aging after installation. At times, acid wash is applied to the stone to etch its surface, which generally dulls the color of the stone. The surface can then be brushed with a mechanical wire bush, making it smooth and restoring the color slightly. Surface roughness can vary from smooth (1/64-1/16”) to somewhat rough (1/16-1/4”), depending on the process.

Learn more about Natural Stone Finishes.

Apex Stone

Uppermost stone in a gable, pediment, vault or dome.


A trim piece under a projecting stone top, stool, etc. See also Driveway Apron.


The curved or pointed construction over a doorway or opening. Arch shapes range from flat to semicircular or semi.


The beam or lowest division of the entablature in the classical orders, spanning from column to column. The decorated surrounds of a window or door at the head and jamb.


A weakly metamorphosed compact rock composed mainly of clay and shale. Used locally as building stone, although rarely produced commercially.


A feldspar-rich sandstone containing 10% or more clastic grains of feldspar. Also called arkosic sandstone and feldspathic sandstone.


A slight, although measurable, chamfer where two surfaces meet. 

Arris Line

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

Artificial Stone

A man-made product attempting to replicate the look of natural stone. This term is actually a misnomer, as it includes an obvious contradiction of terms. Stone is a naturally occurring earth material. See Engineered Stone and Cultured Marble.


A stone façade of generally square or rectangular units having sawed or dressed beds. There are three generally recognized distinctions:

  1. Coursed Ashlar: Ashlar set to form continuous horizontal joints.
  2. Random Ashlar: Ashlar set with stones of varying length and height so that neither vertical nor horizontal joints are continuous.
  3. Stacked Ashlar: Ashlar set to form continuous vertical joints.


ASI (Allied Stone Industries)

The Allied Stone Industries is made up of stone quarriers, fabricators, and the suppliers of natural building materials and related machinery and tools.

Standard terminology relating to dimension stone set by ASTM International.
ASTM International

A consensus standards authoring organization originally founded in 1896 as the American Society for Testing Materials.

AxedWork (British)

Hand-dressed stone surface showing fine-to-course, generally linear tool marks made by an ax, pick or bush hammer.

Created in collaboration with the Natural Stone Institute (NSI).
Copyrights apply.

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