diaclasiten.

/dʌɪˈakləsʌɪt/Etymology: < German diaklas (Breithaupt, 1823), < Greek διακλάειν to break through or asunder; on account of its easy cleavage.
Mineralogy.
1850 J. D. Dana (ed. 3) 268.
This entry has not yet been fully updated (first published 1895; most recently modified version published online June 2018).