Hydroxylclinohumite, a new member of the humite group: Twinning, crystal structure and crystal chemistry of the clinohumite subgroup

✍ Scribed by Ferraris, Giovanni; Prencipe, M.; Sokolova, E.; Gekimyants, V.M.; Spiridonov, E.M.

• Book ID: 115508962
• Publisher: Oldenbourg Wissenschaftsverlag
• Year: 2000
• Tongue: English
• Weight: 162 KB
• Volume: 215
• Category: Article
• ISSN: 2194-4946
• DOI: 10.1524/zkri.2000.215.3.169

✦ Synopsis

Hydroxylclinohumite Mg~9~[SiO~4~]~4~(OH, F)~2~, a new mineral from Zelentsovskaya mine near Magnitka (Zlatoust district, Southwestern Urals), is the OH-dominant equivalent of clinohumite Mg~9~[SiO~4~]~4~(F,OH)~2~. The crystal structure of hydroxylclinohumite has been refined from single-crystal X-ray data to R = 0.026 for the 1912 observed unique reflections [F~o~ > 4σ(F~o~): a = 4.7480(3) Å, b = 10.2730(7) Å, c = 13.6894(2) Å, α = 100.72(1)°, V = 656.1(1) Å^3^, P2~1~/b (No. 14), Z = 2]. Twinning on {001}, which apparently doubles the c axis, was detected and a ratio of 0.94:0.06 between the volumes of the two twin components has been obtained by least-squares refinement. The crystal structure of hydroxylclinohumite corresponds to that of clinohumite except for the positions of the hydrogen atoms. The crystal chemistry of the clinohumite subgroup is discussed and a general formula M^2+^
~8~(M^2+^, M^4+^) (SiO~4~)~4~(OH, F, O)~2~ (M^2+^ and M^4+^ mainly Mg and Ti, respectively) is proposed for it.