There are many polyvalent elements constituting minerals. The atomic valencies of Fe and As in minerals including both of them are +2, +3 and +3, +5, respectively. Scorodite, Fe
3+[As
5+O
4]·2H
2O, seen in oxidized zone of As-bearing metallic ore deposits contains Fe
3+ and As
5+, both of which are in their highest valency states, respectively. The mineral co-exists with parasymplesite, Fe
32+[As
5+O
4]
2·8H
2O, which contains Fe
2+(lowest valency state) and As
5+(highest valency state), as seen in the Kiura mine, Oita Prefecture. However, in the same ore deposit, scorodite co-exists with karibibite, Fe
23+As
43+O
9·1∼2H
2O, too, in which Fe is in the highest and As in the lowest valency states, respectively. Such unreasonable relations seen in discrete two minerals from the same genetical units have eluded our consideration to date.
In case of a single mineral species, karelianite, V
2O
3, a part of V
3+ is substituted by Fe
3+. In aqueous solution naked V
3+ does not co-exist with naked Fe
3+ under room temperature condition. Since this is a metamorphic mineral, it is plausible to ascribe the maintenance of this relation to the possible existence of oxygen-armored cations through the metamorphic process. It is highly desirable to cultivate our ability capable of finding such a point.
Apart from the above discussion, we use the expression that there is a mineralizaiton of arsenic in an ore deposit if any arsenic mineral is concentrated therein. Any discussion is necessary to specify the states of arsenic in this case, where it could behave as anion, cation, or both.
抄録全体を表示