Townendite
Townendite is an IMA-recognized mineral species in the silicate class, with the chemical formula Na₈ZrSi₆O₁₈.
It crystallizes in the hexagonal crystal system (space group R-3m). It is a member of the Lovozerite structural group.
Key properties: Mohs hardness 5–6; specific gravity 2.89; White streak; Vitreous luster; optically uniaxial.
IMA symbol Twn, IMA status: approved, named in 2009.
Found in lujavrite layers of nepheline syenite in a layered alkaline igneous intrusion. Possibly formed as an alteration product of steenstrupine-(Ce).
It is found associated with Albite, microcline, arfvedsonite, monazite, vitusite-(Ce), aegirine, analcime, naujakasite, steenstrupine-(Ce).
The mineral was named to honor Roger Townend (b. 1938), a consulting mineralogist, Perth, Western Australia, for his contributions to mineralogy, particularly related to the Ilímaussaq deposit.