PROCESS OF FORMATION OF As-BEARING MINERALS AND ARSENATES UNDER SURFACE OF THE EARTH

新矿物副砷黄锰矿是天然砷的第三种多晶型物，发现于大分县的向野矿。在日本首次发现了副铝榴石、白榴石、水砷铅矿、白砷铅矿、白砷铅矿和砷砷铅矿。原生含砷矿物多为含硫化合物，蚀变过程中砷被氧化成五价态。三价砷（砷氧化物，所谓亚砷酸）仅作为天然砷的蚀变物质被发现。砷是矿区周围岩石和土壤的常见成分。然而，这种毒性问题并不严重，因为As包含在相对稳定和不溶性的砷酸盐矿物中，即作为五价态As（砷酸盐）。在地表环境下发现的最常见的砷酸盐矿物是臭葱石。它是水合砷酸铁。施威特曼石是低结晶的水合硫酸铁矿物，并且可以包括As。I在水流中很容易形成，然后A在水流中被去除。施氏石稳定后，可转变为FeOOH（主要为针铁矿）+黄钾铁矾+臭葱石。

The new mineral, pararsenolamprite, the third polymorph of native As, was found from the Mukuno mine, Oita Prefecture. Pararealgar, alacranite, dufrenoysite, claudetite, wallkilldellite and arseniopleite are found as the first occurrence in Japan. The primary As-bearing minerals are mostly S-bearing compounds, and As is oxidized to penta-valent state when their minerals were altered. The tri-valent As (arsenic oxide, so called arsenious acid) is only found as the altered material from native As. Around mining areas As is common component of rocks and soils. However, this poisonous problem do not cause seriously, since As is included in relatively stable and insoluble arsenate minerals, that is, as penta-valent state As (arsenate). Most common arsenate mineral found under surface circumstance is scorodite. It is ferric hydrate arsenate. Schwertmannite is low crystalline hydrous ferric sulfate mineral and can include As. I forms easily in stream and then As in stream is removed. When schwertmannite becomes stable state, It may be changed to FeOOH (mostly goethite) + jaroshite + scorodite.