Mineralogical Journal 

About: Mineralogical Journal is an academic journal published by Japan Association of Mineralogical Sciences. The journal publishes majorly in the area(s): Crystal structure & Massif. It has an ISSN identifier of 0544-2540. It is also open access. Over the lifetime, 730 publications have been published receiving 6433 citations. The journal is also known as: Mineralogical journal (Sapporo).

Argon isotope analysis by a newly developed mass spectrometric system for K-Ar dating.

Abstract: A new mass spectrometer and the associated analytical systems, called HIRU, was designed and constructed for the argon isotope analysis of minerals from young volcanic rocks as well as metamorphics and granitoids. HIRU is composed of a sample holder, an extraction oven, purification lines, standard gas lines, a mass spectrometer, and an ultra high vacuum pumping system. All the parts, except for the sample holder, were made of stainless steel and connected with ICF flanges using Cu gaskets or ultra high vacuum metal valves. The mass spectrometer is a 15cm sector type with an oblique incidence-single focusing system using an electron bombard ion source and three collectors which contain 8 (for 36Ar), 6 (38Ar) and 4 (40Ar) stage secondary electron multipliers respectively.Argon isotope analysis by HIRU is summarized and the precision and reliability of the new mass spectrometric system are discussed in this paper. A series of analysis for argon isotopes, such as taking a set of spectrum, the calculation of isotopic ratios, argon content, and ages is carried out with a computer-controlled system. HIRU has mde it possible to date geological materials with high sensitivity (eg. tens mg of mica of Cretaceous age), high precision (ca. 1% of error for argon content), reliability (possible for rocks older than 0.1 Ma), and convenience (eg. 5–6 samples can be dated per day).

X-RAY STUDY ON THE ^|^alpha;-^|^beta; TRANSITION OF Ag2S

Abstract: The refinement of the structure of a-Ag2S was undertaken together with an accurate determination of the lattice constants. The final structure gave the R-factor of 16.8% including unobservable reflections. The crystals found in nature are almost invariably twinned, and a theoretical consideration on the modes of twinning led to the conclusion that twenty-eight twin laws are possible. Heat treatments of the specimens were carried out in order to know the details of the progress of twin formation premonitory to the a-9 transition. The specimens remain substantially unaltered up to 152-156•Ž, the only change being observed in the ƒÀ-angle. Above this temperature range, individuals of twins in various orientations appear, and the X-ray reflections take an appearance of trains of spots. At about 165•Ž these spots along each line fuse into one another, giving an arc-like intensity distribution. Some nodes of strong intensities along these arcs are converted into sharp reflections of the high-temperature form at the transition temperature, 173•Ž. As the rise of temperature, therefore, the structure of Ag2S makes the first approach to the ƒÀ-form by giving itself more maked cubicity through the change in the ƒÀ-angle, at the next step simulates the symmetry of the high-temperature form by twinning, and finally at the transition temperature rearranges into parallel orientation the twin individuals which have been deranged owing to their obliquity.

Nomenclature of pyroxenes

Abstract: This is the final report on the nomenclature of pyroxenes by the Subcommittee on Pyroxenes established by the Commission on New Minerals and Mineral Names of the International Mineralogical Association. The recommendations of the Subcommittee as put forward in this report have been formally accepted by the Commission. Accepted and widely used names have been chemically defined, by combining new and conventional methods, to agree as far as possible with the consensus of present use. Twenty names are formally accepted, among which thirteen are used to represent the end-members of definite chemical compositions. In common binary solid-solution series, species names are given to the two end-members by the “50% rule”. Adjectival modifiers for pyroxene mineral names are defined to indicate unusual amounts of chemical constituents. This report includes a list of 105 previously used pyroxene names that have been formally discarded by the Commission.

Tobelite, a new ammonium dioctahedral mica

Abstract: Mineralogical properties of tobelite, a new ammonium-dominant dioctahedral mica, found in the Ohgidani pottery stone deposit at Tobe, Ehime Prefecture, Japan, are described.This mineral, accompanied by quartz, occurs as a hydrothermal alteration product of a biotite andesite dyke. Wet chemical analysis gives a structural formula: ((NH4)0.53K0.19Na0.01 0.27)1.00 (Al1.97Ti0.00Fe3+0.03Mg0.05)2.05(Si3.17Al0.83)4.00O10(OH)2. The low interlayer charge is explained with its poorly crystallized nature. The X-ray powder diffraction pattern is very close to that of synthetic NH4Al2Si3AlO10(OH)2 by Eugster and Munoz (1966), and is satisfactorily indexed on 1M polytype cell having a=5.219A, b=8.986A, c=10.447A and β=101.31°. Space group may be C2⁄m. Tobelite is characterized by its larger unit layer thickness (10.25A) than that of potassium dioctahedral mica. This material yields an endothermic reaction and absorption bands specific to ammonium in DTA curve and infrared spectrum, respectively. Optically it is biaxial, negative, 2Vcalc.=28°. Refractive indices are α=1.555, β=1.575, γ=1.581, all±0.002.Mineralogical description is made also on tobelite from the Horo pyrophyllite deposit, Hiroshima Prefecture, Japan, which is well crystallized as compared with the Tobe material and is tentatively determined to be of 2M2 polytype.

THE CRYSTAL STRUCTURE OF ORPIMENT (As2S3) REFINED

Abstract: The crystal structure of orpiment, AS2':33, was refined by the Fourier syn. thesis. The unit cell has the dimensions, a=11.46 A, b=9.57 A, c=4.22 A ane ~=90.5°, containing four AS2':33. The space group is dh-P2t!n. The structun is essentially the same as one described earlier. lntroductz'on In the original analysis of orpiment, the usual trial.and-error method was used?). The crystal structure of realgar determined subsequently by the inequality relations and Fourier synthesis is considered much more precise. The relationship between these two related minerals has been discussed already6>. The present study was undertaken in order to refine the atomic parameters of orpiment by means of the Fourier analysis, so that our discussion might be based on much more balanced data.