Armstrongite

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Armstrongite is a silicate mineral with the formula CaZr[Si6O15]·3H2O. It belongs to the monoclinic crystal system and is typically dark to light brown. It cleaves perfectly on {001} and has good cleavage on {100}; it is very brittle. It has a hardness of 4.5 on the Mohs scale, a vitreous luster, a brownish-white streak, and is translucent. Armstrongite was first described in 1973 from the Dorozhnyi pegmatite in Khanbogd District, Ömnögovi Province, Mongolia, and it is named after American astronaut Neil Armstrong.