Understanding Stone Classifications

Nearly all stones from marble to granite are given a classification of one type or another. This could be a letter grade or a usage recommendation, and these classifications can vary from one manufacturer or stone yard to another. Understanding what some of the more commonly used systems mean can help homeowners choose the right stone for the right application.

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Most stones are graded at the quarry for their color, clarity, and strength. Stones that are consistent in color with few inclusions, fissures, or pits are usually graded with an A. These stones are often denser and more durable than others marked B through D. Stones that are graded at the other end of the spectrum as a D are usually more varied in color, with noticeable fissures, pits, or inclusions. A stone graded A is much less likely to break or crack than a stone graded D. Stones with grades in between these two may have any mixture of veining, color variation, and small fissures or pits.

Some stones may also be graded as residential or commercial. This can be misleading because each of those groups could mean one of two things. If the rating refers to color and veining, residential stones are the nicer, more evenly toned selections. If the rating refers to strength, however, then the commercial stones are the more durable, with residential stones being further broken down into light and heavy residential use.

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Many stones are also graded just for color, with common classifications being:

  • Select, which means the stone that is homogeneous, with light color, and few veins
  • Standard, which means the stone is homogeneous, with normal veins
  • Classico, which means the stone is not homogeneous (spots, shadows…), and more veined

Stones that are graded standard or classico may also be graded A or commercial for strength, which further makes the issue confusing. Homeowners should determine what it is they want from their stone, so they can make the correct decision of strength or color to get the right material for them.

 

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