Sue Bartlett, age 13, of Fayetteville, Ga., for her question.

WHAT EXACTLY IS MARBLE?

Waxy white marble is classed as a metamorphic mineral, which means it has been altered by drastic remodeling. originally it was a deposit of limestone, built from the calcium remains of tiny sea dwellers. Deposits of this sort cover vast areas of the ocean floor, and more are being added by fossilized material all the time. Here and there an old sea bed was lifted above the water, and limestone deposits became part of the dry land.

In some regions the earth's crust was remodeled, perhaps by volcanoes and mountain building. Heat and pressure transformed the crystal structures of many minerals  and the old limestone deposit was remade into a lovely layer of waxy marble

Sometimes it was tinted with traces of mineral impurities. Often scraps of organic material were added, and the waxy white was streaked with dark veins.