| Rating | Solver | Clue |
|---|---|---|
| CHALK | White limestone | |
| NITROCALCITE | Nitrate of calcium, a substance having a grayish white color, occuring in efforescences on old walls, and in limestone caves, especially where there exists decaying animal matter. | |
| DOLOMITE | ... limestone, often crystalline granular, either white or clouded. It includes much of the common white marble. Also called bitter spar. ... | |
| LIME | Oxide of calcium; the white or gray, caustic substance, usually called quicklime, obtained by calcining limestone or shells, the heat driving o... | |
| MARBLE | ...e, capable of being polished and used for architectural and ornamental purposes. The color varies from white to black, being sometimes yellow, r... | |