31 0 0 0 茨城県日立市日立鉱山から発見された新鉱物・日立鉱
- 著者
- 栗林 貴弘
- 出版者
- 一般社団法人 日本鉱物科学会
- 雑誌
- 岩石鉱物科学 (ISSN:1345630X)
- 巻号頁・発行日
- pp.210115, (Released:2021-04-14)
Hitachiite (IMA2018-027), ideally Pb5Bi2Te2S6, has been discovered from the Hitachi mine, Ibaraki Prefecture, Japan. Hitachiite commonly occurs as small size of crystals (∼ 30-50 μm) with euhedral hexagonal plate form within pyrite crystals, and co-exists with pyrite, chalcopyrite, sphalerite, pyrrhotite, and galena. Hitachiite shows a metallic luster and black streak, and its macroscopic color is silver grey. Hitachiite has a Mohs' hardness of 2½-3, and its calculated density is 7.54 g/cm3. The discovered hitachiite has trigonal symmetry with a = 4.2200(13) Å, c = 27.02(4) Å. Its space group is P3m1. Hitachiite has a layer-type structure based on ABC-type closed packing of each single element atomic sheet stacked along the c-axis. The stacking sequence is -Te-Bi-S-Pb-S-Pb-S-Pb-S-Pb-S-Pb-S-Bi-Te- (15 layers). It is possible that hitachiite would be forming a homologous series expressed as Bi2Te2S・nPbS with tetradymite (n = 0), aleksite (n = 1), and suddlebackite (n = 2).
3 0 0 0 OA 奈良県天川村産レインボーガーネットにみられるラメラ組織の特徴
- 著者
- 中村 友梨江 長瀬 敏郎 栗林 貴弘 今井 裕之
- 出版者
- 一般社団法人日本鉱物科学会
- 雑誌
- 日本鉱物科学会年会講演要旨集 日本鉱物科学会 2017年年会
- 巻号頁・発行日
- pp.41, 2017 (Released:2020-01-16)
昨年の年会にて結晶構造を報告した奈良県天川村産のレインボーガーネットについて,詳細な内部組織の観察からラメラ組織の成因を議論することを目的とし,薄片及び研磨片を電解放出型走査電子顕微鏡で観察した.Fine lamellaeはほぼアンドラダイト端成分の層とAlに富む層からなり,先行研究と同様に各層の幅には周期的な変化がみられた.幅が変化する場所はwavy lamellaeに一致する.また,fine lamellaeは幅が変化するところでクランク状に折れ曲がっており,結晶表面に対する高さが1周期分だけ変化する.これらの観察結果からwavy lamellae はfine lamellaeの厚さの変化によるモアレであること,fine lamellaeは平坦ではなく結晶面に対して山なりで階段状の斜面になっていることが明らかになった.さらにfine lamellaeがセクター境界の両側で一対一に対応しており,境界を越えて連続していることからfine lamellaeは成長縞であり,その形状はガーネットが成長したある時点での結晶表面の形状を反映していると考えられる.
1 0 0 0 OA 青森県津軽地域の碧玉(津軽にしき石)の組織と成因について
- 著者
- 長瀬 敏郎 石川 志緒利 栗林 貴弘
- 出版者
- 一般社団法人 日本鉱物科学会
- 雑誌
- 岩石鉱物科学 (ISSN:1345630X)
- 巻号頁・発行日
- vol.47, no.3, pp.127-140, 2018 (Released:2018-11-17)
- 参考文献数
- 56
Nishiki-ishi is a kind of jasper and shows mixed bright red, yellow-brown, green, and black colors. It occurs in Tsugaru region, Aomori Prefecture Japan and has been used for ornaments. Most of the raw stones are usually collected at shingle beaches, and few outcrops of the jasper are found out. Therefore, the occurrence of Nishiki-ishi has not been reported in detail. To elucidate the formation process of Nishiki-ishi, we observed textures of the rocks and minerals by optical and electron microscopes, Raman spectroscopy and analyzed the chemical compositions of minerals by an electron micro-probe analyzer. Nishiki-ishi were collected from two localities: Aoiwa, Nakadomari-machi, Kita-Tsugaru and Tappi-zaki, Sotogahama, Higashi-Tsugaru, Aomori Prefecture, Japan. It mainly consists of mixtures of micro-crystalline and crypto-crystalline quartz, opal-CT and iron-containing minerals. Its colors are caused by iron-containing minerals; hematite (red), celadonite (green), goethite (yellow), siderite (yellow), pyrite (black), and marcasite (black). These iron-containing minerals, which exhibit needle-like or granular forms, are included as fine grains in quartz crystal and fill boundaries among the quartz crystals. The macroscopic structure of Nishiki-ishi is breccia-like or clastic. In the texture, breccia fragments show yellow or red colors, and green and black parts filled up the space between breccia fragments. Yellow-brown and red color parts of Nishiki-ishi have flamboyant and mosaic (jigsaw) textures, which consist of micro-quartz and optically length-slow type spherules of quartz. Black and green color parts are also composed of opal-CT, chalcedony, and micro-quartz. These features are considerable differences of quartz textures between in brecciated fragments and at the matrix among brecciated fragments. Nishiki-ishi was formed by silicification of volcanic rocks during volcanic activity. After the silicified rocks brecciated, quartz and chalcedony precipitated in the breccia.