Dark green crystals of the vare zirconium mineral armstrongite from the type locality in Mongolia (Khan-Bogdo Massif, Gobi Desert, Mongolia) and one of the only 4 confirmed locality worldwide. Armstrongite was named after the first man who landed on the Moon in 1969, Neil Armstrong. — Photo: David Hospital · CC BY-SA 4.0
Armstrongite
Armstrongite is an IMA-recognized mineral species in the silicate class, with the chemical formula CaZr(Si₆O₁₅)·2H₂O.
It crystallizes in the monoclinic crystal system (space group C2/m).
Key properties: Mohs hardness 4.6; specific gravity 2.56–2.59; Vitreous luster; optically biaxial.
IMA symbol Asg, IMA status: approved, named in 1972.
Found in schlieren of alkalic granite pegmatite, at the contact of arfvedsonite-bearing granite with xenoliths of felsic volcanic rock.
It is found associated with Elpidite, quartz, microcline, albite, aegirine, arfvedsonite, monazite, synchesite, titanite, other titanosilicates (Khan-Bogdo); elpidite.
The mineral was named to honor Neil Alden Armstrong (1930-2012), American astronaut, first man to walk on the Moon.