diatom

/ˈdaɪəˌtɑm/

IPA: /D AY0 AH0 T AA1 M/

noun
  1. 1

    Any of a group of minute unicellular algae having a siliceous covering of great delicacy, now categorized as class Diatomophyceae or division Bacillariophyta.

Source: https://en.wiktionary.org/wiki/diatom