Meerschum or Meerschaum: How To spell?

The word Meerschum is misspelled against Meerschaum, a noun meaning "A fine white claylike mineral, soft, and light enough when in dry masses to float in water. It is a hydrous silicate of magnesia, and is obtained chiefly in Asia Minor. It is manufacturd into tobacco pipes, cigar holders, etc. Also called sepiolite."