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

新矿物pararsenolamprite是在大分县Mukuno矿发现的原生砷的第三个多晶型。在日本首次发现副藻石、钠长石、榴辉石、长辉石、壁辉石和砷杂岩。原生含砷矿物多为含s化合物，当其矿物发生改变时，砷被氧化成五价态。三价砷（即氧化砷，又称亚砷酸）仅作为天然砷的改变物被发现。在矿区周围，砷是岩石和土壤的常见成分。然而，由于砷以五价态砷（砷酸盐）的形式存在于相对稳定且不溶的砷酸盐矿物中，所以不会造成严重的毒性问题。在地表环境下发现的最常见的砷酸盐矿物是铁榴石。它是水合砷酸铁。许氏锰矿是一种低结晶水合硫酸铁矿物，可含砷。I在流中容易形成，然后流中的As被去除。当schwertmanite达到稳定状态时，它可能变成FeOOH（主要是针铁矿）+黄钾石+铁长石。

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.