There are over eight thousand types of marble on the market today, and the number continues to grow. It would be impossible to list every available type, but there are some common characteristics that make it fairly easy to identify marble. Marble is commercially defined as any limestone that will take a polish. Limestones, and therefore marbles, are composed of minerals of calcite or dolomite. Marble in its purest state is white; colored marbles are the result of other minerals being mixed with the calcite or dolomite. There are some other commonly recognizable characteristics:

• Marble, no matter what the color, will usually have some type of veining running through it; the veins are usually different in color than the main color of the stone. There are, however, exceptions to this rule. Some marbles, such as Thassos White will exhibit little or no veining.  
• Marble is relatively soft when compared to other stones, such as granite. It will scratch very easily. If you run a knife blade lightly across the surface of the stone and it leaves a scratch, you are very likely to be dealing with marble. Warning: do not attempt this in the middle of your floor, if at all. If you need to determine how easily it will scratch, pick an inconspicuous spot, such as in a closet, under a carpet, etc. On dark marbles, these scratches will appear as light lines on the surface of the stone; on lighter-colored marbles it may be difficult to detect a scratch.
• Marble is also very sensitive to acidic chemicals. Vinegar, for example, is acidic, and will leave a dull spot on marble. It is extremely important to keep any marble surface out of contact with the following acidic materials: lemon, tomato and tomato sauce, bleach, coffee, fruit juices, wine, urine, vomit, tile cleaners like Tile X, the various mildew removers, X-14, acidic toilet bowl cleaners, cleaners containing lemon, pool pH decrease (muriatic acid), driveway cleaners, and, as noted, vinegar. Most products that contain acids will have their ingredients listed on the label.