New mineral kôzulite belongs to the alkali amphibole group in which manganese (II) is the predominant cation of the Y-position. The mineral occurs as banded aggregate of short prismatic crystala with the faces of b, m and r up to 3.5×2.0×1.5mm in size, in the bedded magnanese deposit of Tanohata Mine, Iwate Prefecture, Japan, in the highly metamorphosed Jurassic chert-hornfels by the intrusion of granodiorite. Associated minerals are braunite, rhodonite, manganiferou alkali pyroxene, manganiferou alkali amphibole and quartz.
Color reddish black to black, streak light purplish brown, luter vitreous, H. 5, G. measured 3.30, calculated 3.36. Cleavage (110) perfect. Optically biaxial negative, ns α=1.685, β=1.717(mean), γ=1.720, 2Vα=34-36°, cΛX=25°. Strongly pleochroic with X yellow-brown, Y reddish brown, Z dark brown, absorption Z⟩Y⟩X, dispersion very weak, probably r⟩v.
Chemical analysis gave SiO₂ 51.38, TiO₂ none, Al₂O₃ 1.69, Fe₂O₃ 2.85, FeO none, MnO 27.96, ZnO 0.03, MgO 2.71, CaO 1.12, BaO none, Na₂O 8.41, K₂O 1.36, H₂O (-) 0.06, F 0.08, sum 99.75-O (=F₂) 0.03=99.72%, corresponding to (Na_2.54 K_0.27 Ca_0.19)_3.00 [(Mn_3.69 Mg_0.63)_4.32 (Fe⁺³_0.33Al_0.31)_0.64]_4.96Si_8.00O_21.78[(OH)_2.18F_0.04]_2.22, as O+OH+F=24.
The x-ray powder data showed the mineral to be monoclinic with a₀=9.91, b₀=18.13, c₀=5.28Å, β=104.5° and precession photographs of the same specimens by N. Morimoto, Osaka University, showed it to be monoclinic, space group C2/m, a=9.91±0.02, b=18.11±0.04, c=5.30±0.02Å, β=104.6°±0.1°, Z=2. The strongest x-ray lines are 8.51 (100) (110), (4.52) (10) (040), 3.40 (10) (131), 3.29 (17) (240), 3.15 (67) (310), 2.96 (6) (221), 2.827 (31) (330), 2.748 (8) (331), 2.722 (10) (151), 2.602 (6) (061), 2.545 (6) (202), 2.349 (7) (351), 2.174 (9) (261), 1.908 (7) (510), 1.447 (7) (661). The high-temperature x-ray study and DTA indicate that the mineral breaks down to braunit plus glas at about 950°C.
The name is for late Dr. Shukusuke Kôzu (1880-1955), formerly Professor in Tohoku University, Japan who made many contributions to the study of rock forming minerals. Type material is preserved at Tohoku University.
The mineral and name were approved before publication by the Commission on New Minerals and Mineral Names, IMA.

View full abstract

Fine crystals of gyrolite were found in druses of Irakawa olivine dolerite, Yamagata Prefecture where the occurrence had been reported by Sakurai (1962). Coexisting minerals were analcite, thomsonite, natrolite and opaline silica. The result of chemical analysis indicates that Ca/Si is almost equal to 2/3. X-ray powder pattern of Irakawa gyrolite shows weak peaks of truscottite.
New occurrence of gyrolite associated with analcite and calcite were also found from basaltic tuff breccia at Otemo, Niigata Prefecture. X-ray powder pattern shows that the sample contains no other sheet silicate such as truscottite.
The c-periods of these gyrolites convert from 22.26À to 19.6À at about 400°C on the consequence of one layer dehydration for each unite layer.

View full abstract

The Nibetu district is composed of the basement granites, the Tertiary granite, and Tertiary volcanic rocks. The basement granites are called the Taiheisan pluton. The Tertiary volcanic rocks are the Haginari propylite, the Sunakobuchi basalt, and the Manaitayama andesitic volcanic rocks.
The Tertiary granite mass is 4×4km² in area. It is composed of micro-quartz-diorite, trondhjemitic porphyry, granite-porphyry, and granophyre. The Tertiary granite was intruded into the Haginari formation and basement granites, along a certain sheared zone, probably at the post-Haginari stage, and caused contact metamorphism to the Haginari propylite lava and meta-diabase dykes.
The contact aureole around the mass is divided into the following two zone.
(I) Epidote-chlorite-actinolite zone.
(II) Epidote-actinolite-biotite zone.
Besides, garnet and hornblend are found at the very contact.

View full abstract