bone ash

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. The white, powdery calcium phosphate ash of burned bones, used as a fertilizer, in making ceramics, and in cleaning and polishing compounds.

Century Dictionary and Cyclopedia

1. n. Same as bone-earth.

Wiktionary

1. n. The white, powdery ash left when bone is burnt; it is high in calcium phosphate and is used as a fertilizer and in making bone china.

GNU Webster's 1913

1. n. burnt powered; bone earth.
2. n. the residue from calcined bones; -- used for making cupels, and for cleaning jewelry.

WordNet 3.0

1. n. ash left when bones burn; high in calcium phosphate; used as fertilizer and in bone china