This is the polished brown armstrongite specimen with aegirine and feldspar. Dimensions: 1.8 x 1.2 x 0.6″ (4.5 x 3 x 1.6cm). Weight – 1oz (28 grams). Origin: Mongolia.
Some information about armstrongite:
Armstrongite is a very rare mineral, layered zirconium silicate CaZr [Si6O15] × 5H2O. Forms crystals up to 2 cm and their aggregates; coarse-grained aggregates and accumulations up to 50 cm. Monoclinic system. Color is dark to light brown, luster is glassy. It is very fragile.
Found in alkaline granites, in association with aegirine in pegmatites of the Bogdo Khan massif (Khan-Bogdinsky massif), Gobi desert, Southern Mongolia; a little bit in Canada.
The mineral is named after N. Armstrong (Neil Alden Armstrong, 1930-2012), the American astronaut who was the first to reach the lunar surface.