Percoco Marble
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Glossary of Stone Industry Terms

This glossary is limited to terms used on this website (and not already explained where used). Some of the terms include extra information on how that affects your finished stone products and/or our warranty. Some of the definitions come from copyrighted material (© by Marble Institute of America) used with permission.

A

Arris
A small chamfer of approximately 1/16" x 1/16" (1.5 x 1.5 mm) used to eliminate small chips and razor sharp edges.

C

Chips
Chips can occur in stones either as result of sawing operations or handling and restraint devices. Particularly in the igneous stone varieties, the exiting portion of the diamond blade will create many small chips. An arris can be used to eliminate most of these small chips. The use of an arris will make the seam appear wider than its actual dimension when filled. Larger chips may be repaired with epoxy or polyester resin if the completed repair is consistent in color and texture with unrepaired areas of the slab. In many materials, the resin used in the repair will appear more natural if it is not dyed.
Cracks
A man-made break, split, fracture, separation, cleavage, or elongated narrow opening, visible without magnification to the human eye and extending from the surface into the stone, which must extend through the grain or matrix of the stone. Cracks occur in stones as a result of mechanically induced stresses (ie man-made) during handling, fabrication, transport, or installation.

D

Dimension (Dimensional) Stone
A natural stone product that has been cut, machined, and/or finished to specific size or shape. This includes countertops, sculpted fireplace surrounds, flat fireplace surrounds, tables, etc, pretty much anything a stone fabrication shop (such as ourselves) produces.

F

Fissure
An industry term describing any naturally occurring separation along crystalline boundaries visible in exposed surface of the stone. Note that the industry use of this term is different than the scientific, geological use of this term. A fissure is defined by the American Geological Institute as "an extensive crack, break, or fracture in the rock, which may contain mineral-bearing material ."

P

Pits/Pitting
Pitting of the countertop surface, particularly in granite material, is a commonly seen characteristic on natural stone. Granites are made up of several different minerals, each mineral having a different hardness. Granites contain quartz, feldspars, biotite, amphibole, ferrous titanium oxides, and other mineral combinations. On the Mohs Scale, diamonds are the hardest mineral, with a rating of 10. Quartz and feldspar have a hardness of 6.5 to 7 and are very durable. Biotite (small, black minerals throughout the slab) on the other hand is very soft (2. 5) and flakes easily. All true granites have biotite in their composition. Because, biotite is relatively soft and flaky, the first few layers are removed during the polishing process, causing pits throughout the slab. Some granites have more biotite throughout their composition than others. The higher the biotite content of the stone, the more pits it will have. Most polished igneous rocks will have varying degrees of pits, depending on the amount of biotite, muscovite, and phlogopite in their composition. The pits do not make the granite less durable or otherwise inferior, and do not in themselves qualify the slab for replacement . Pits are common in all granites and should be expected when dealing with a natural, polished stone containing several types of minerals with different hardnesses. It is usually best to not attempt repair of pits, as most repair techniques will not cosmetically improve the countertop.