Mt. St. Hilare, Quebec, Canada. Link to MinDat.org Location Data.
Name Origin:
Named for Joseph Desire Hubert Donnay (1902-1994), Belgian-American-Canadian crystallographer and minereralogist and Gabrielle (Hamburger) Donnay (1920-1987), American Canadian mine ralogist, McGill Univeristy.
CI meas= 0.005 (Superior) - where the CI = (1-KPDmeas/KC) CI calc= -0.02 (Excellent) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.1919,KPDmeas= 0.1873,KC= 0.1882 Ncalc = 1.61 - 1.62