Duden, Das große Fremdwörterbuch:
Diatomit [auch mit] der [...] ein Sedimentgestain aus verfestigtem Diatomeenschlamm

http://www.wissen.de/wde/generator/wissen/res...
Diatomit
[der]
poröses, toniges Diatomeengestein, technisch zur Wärmeisolierung verwendet.

http://lexikon.meyers.de/meyers/Diatomit
Diatomit [griechisch] der,
1) Bautechnik: aus Kieselgur hart gebrannter, feuerfester Formstein mit guter Wärmedämmung.
2) Geologie: Bezeichnung für verfestigte diatomeenreiche kieselige Sedimente, auch für Kieselgur.

"diatomite." Webster's Third New International Dictionary, Unabridged. Merriam-Webster, 2002. http://unabridged.merriam-webster.com (31 May 2008).
Main Entry: di·at·o·mite
Function: noun
: a light friable siliceous material resembling chalk that is derived chiefly from the remains of diatoms and is used as a filter aid, adsorbent, filler (as for paints and plastics), and abrasive, and for thermal insulation -- called also diatomaceous earth; compare KIESELGUHR, TRIPOLI

http://www.bartleby.com/61/15/D0201500.html
The American Heritage® Dictionary of the English Language: Fourth Edition.
diatomite
NOUN: A fine, powdered diatomaceous earth used in industry as a filler, a filtering agent, an absorbent, a clarifier, and an insulator. Also called kieselguhr.

http://www.macquariedictionary.com.au
The Macquarie Dictionary
diatomaceous earth
noun a fine siliceous earth composed chiefly of cell walls of diatoms, used in filtration, as an abrasive, etc.; kieselguhr. Also, diatomite

LEO kennt bereits "diatomite = Kieselgur".