The Collaborative International Dictionary of English v.0.48:

diatomaceous \di`a*to*ma"ceous\
   (d[imac]`[.a]*t[-o]*m[=a]"sh[u^]s), a. [See Diatomous.]
   consisting of or containing diatoms or their fossils; as,
   diatomaceous earth (used as a component of dynamite).
   [PJC]