Rengeite, Sr₄ZrTi₄Si₄O₂₂, a new mineral, the Sr-Zr analogue of perrierite from the Itoigawa-Ohmi district, Niigata Prefecture, central Japan

Abstract

is a new member of the perrierite-chevkinite group found in the jades from the Itoigawa-Ohmi district, central Japan. It is monoclinic, P2 1 /a, a = 13.97(1), b = 5.675 (7), c = 11.98(1) A Ê , b = 114.26 (8)8, V = 866 A Ê 3 and Z = 2. The six strongest lines in the X-ray powder diffraction pattern are 3.12 (s) (40-3), 3.05 (vvs) (31-3), 2.99 (vs) (311), 2.84 (s) (020), 2.74 (s) (004), 2.20 (s) (31-5). Electron microprobe analysis gave SiO 2 22.58, TiO 2 29.88, ZrO 2 9.49, Nb 2 O 5 0.24, Ta 2 O 5 0.07, Al 2 O 3 0.20, FeO 0.10, CaO 0.43, SrO 34.32, BaO 0.13, La 2 O 3 0.00, Ce 2 O 3 0.38, Pr 2 O 3 0.10, Nd 2 O 3 0.29, Sm 2 O 3 0.04, total 98.25 wt.%, corresponding to on the basis of O = 22.The unitcell parameters and chemical composition imply that rengeite is the Sr and Zr-analogue of perrierite or high-b analogue of strontiochevkinite. It is transparent, dark brown with adamantine lustre. Its streak is pale greenish brown, and no cleavage was observed. The hardness is VHN 100 606 698 kg mm 2 (Mohs 5 5.5). The calculated density is 4.12 g cm 3 . It is strongly pleochroic from pale green to pale greenish brown where the REE contents are <1 wt.% and pale violet to greenish brown where the REE contents are between 3 and 10 wt.%. It occurs as anhedral grains in close association with titanite, zircon and tausonite in a pebble of blue titanian omphacite-jadeite rock from the seashore of Oyashirazu, Ohmi Town, in a boulder of lavender-coloured Ti-bearing jadeitite from the bed of the Kotaki-gawa river, Itoigawa City, and in a boulder of green jade from the bed of the Hime-kawa river, Itoigawa City, Niigata Prefecture, central Japan. Rengeite is considered to have crystallized by interaction between pre-existing minerals (rutile, anatase, titanite and zircon) and Sr-rich metamorphic fluid during later stage activity of high-P/T metamorphism. The name is for Mt. Renge near the locality and the Renge metamorphic belt where jadeitite deposits are found.

In–situ U–Pb zircon age dating deciphering the formation event of the omphacite growth over relict edenitic pargasite in omphacite–bearing jadeitite of the Itoigawa–Omi area of the Hida–Gaien belt, central Japan

“…Natrolite jadeitite (Miyajima et al, 1999) and analcime jadeitite (Ishida et al, 2005;Morishita et al, 2007) are not uncommon in this area. Euhedral jadeite grains were found in albite, natrolite, and analcime matrices in each jadeitite sample (e.g., Miyajima et al, 1999 (Miyajima et al, 2001), and matsubaraite with an ideal formula of Sr 4 Ti 5 (Si 2 O 7 ) 2 O 8 , have been found in jadeitite, and will be called new Sr-Ti-Zr minerals in this paper. Thus, a hydrothermal origin has been proposed for jadeitite in this area (Miyajima et al, 1999;Kunugiza et al, 2000;Morishita et al, 2007).…”

Phase relation in the NaAlSiO₄–SiO₂–H₂O system for the hydrothermal precipitation of jadeite, albite, natrolite, and analcime in jadeitite of the Itoigawa–Omi area, Japan

“…In the presence of such a fluid, a straight tie line connecting H 2 O-analcime-jadeite becomes a triangle of fluid-analcime-jadeite in the somewhat distorted triangle of the NaAlSiO 4 -SiO 2 -multicomponet fluid system, from which analcime and jadeite can be precipitated. If the hydrothermal fluid precipitated jadeite, albite, natrolite and analcime, the more evolved fluid might precipitate new Sr-Ti-Zr minerals (Miyajima et al, 1999(Miyajima et al, , 2001 and Ba-feldspar lately (Morishita, 2005). The jadeite-analcime rock of this study contains stronalsite, in addition (Fig.…”

Graphite–3R in a fault fracture zone associated with black jadeitite from Kanayamadani, Itoigawa, central Japan

“…The main jadeitite localities in the Renge Metamorphic belt include Ohmi, Hashidate, and Kanayamadani (Kawano, 1939;Chihara, 1958). The formation of jadeite in this region has been attributed to various causes, but recent studies have begun to explore the potential hydrothermal effects on jadeite formation (Miyajima et al, 1999(Miyajima et al, , 2001(Miyajima et al, , 2002(Miyajima et al, , 2003Morishita, 2005). Varieties of jadeitite found in this region are white, blue, lavender, green, and black (Iwao, 1953;Chihara, 1971Chihara, , 1987Chihara, , 1989Oba et al, 1992;Miyajima et al, 1997Miyajima et al, , 2001Miyajima et al, , 2004Miyajima et al, , 2005Smith and Gendron, 1997).…”