Comparing Granite to Other Memorial and Sign Materials
All Stone is not Alike
There are several different types of stone. The most common are granite, marble,
limestone, travertine and sandstone. Each stone has unique physical characteristics, which affect its applicability to various designs. This section describes the characteristics and physical properties of the major
Granite is an igneous rock created deep within the earth from magma, cooled slowly under great pressure. It is the hardest memorial and sign stone with very
dense grain, making it virtually impervious to stain. It takes a highly polished finish, which will endure even in inclement environments. It also can be finished in a
variety of other ways. There is a broad spectrum of granite colors ranging from nearly pure white to nearly pure black. During its formation, granite may also have
been infused with other minerals providing patterned "movement" as well as color.
Marble is a metamorphic rock, composed of metamorphosized limestone. In its purest form, marble is crystalline white calcite. Most marbles, however, are
infused with impurities such as dolomite, silica or clay, providing variations in color and significant movement. The base colors of marble range from white to
black with a broad range of hues. Marble is significantly softer than granite and therefore subject to greater wear and weathering.
Limestone is a sedimentary rock composed of calcites and dolomites. Organic limestone's were formed from the deposits of marine shellfish and fossils.
Limestone is non crystalline and possesses very uniform composition, texture and structure. It is soft and therefore easy to quarry and shape. Limestone ranges in color from white to gray and does not take a polish.
Travertine displays characteristics similar to limestone. It is layered calcium carbonate formed by water deposits from spring water, particularly hot springs.
Metamorphosized travertine is marble-like and can take a polish.
Sandstone is a sedimentary rock made of compacted sand, held together with
calcium, silicon or ferrous minerals. Sandstone varies in color, from red to yellow to white, based on the presence of other minerals. Sandstone is soft and easy to
quarry and shape. It is susceptible to erosion and deterioration from air pollutants. Brownstone is a variety of sandstone.
Stone generally weathers better than other building materials; however, not all stone endures equally well. Some are subject to greater damage from freezing
and thawing and attack from sulfurous and sulfuric acid, carbonic acid and ammonium salts. Granite is nearly impervious to weathering from temperature
changes and from airborne chemicals. In fact, granite is so resistant to chemical erosion that granite tanks are often used to store highly caustic materials.
Freeze/thaw weathering rarely occurs in polished granite surfaces. Granites with thermal finishes are slightly more permeable and can experience minor
freeze/thaw weathering in the top quarter-inch of finish. However, weather damage to granite with any finish is extremely uncommon because of its inherently low absorption rate.
Granite is very consistent in color and texture when compared to marble, for example; however, granite also exhibits movement and color variation.