Analcime

Formula: Na(AlSi2O6) · H2O
According to the International Zeolite Association (http://www.iza-online.org/natural/Datasheets/Analcime/Analcime.html) the mineral has variable composition, that can be given as Na16-x(H2O)16+x[Al16-xSi32+xO96], with x varying from -3.4 to +4.3. The Na content generally is ~16 atoms per formula unit, but may range from 12 to 17. Si ranges from 28.6 to 36.3.
Colour: White, colourless, gray, pink, green, yellow
Lustre: Vitreous, Sub-Vitreous, Dull
Hardness: 5 – 5½
Specific Gravity: 2.24 – 2.29
Crystal System: Triclinic
Member of: Zeolite Group