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MINERALS INDEX
FRIEDELITE GROUP
R8(OH,Cl)x(As2O5)y(SiO3)6.3H2O
Although the minerals of the friedelite group are rare at Franklin, the group is well represented numerically, as 3 species have been found there, 2 of which are not known elsewhere. Mcgovernite, for which a satisfactory formula has not been derived, although chemically rather different from the minerals of the group, is nevertheless a basic arseniosilicate and seems to be akin to the group in its optical properties, so it is provisionally included therein. Pyrosmalite, so far not reported from Franklin, is included to show the parallel relations of friedelite and pyrosmalite and of schallerite and ferroschallerite. The following tabular statement brings out the chemical affinities of the group.
| Friedelite | Mn8(OH,Cl)4(SiO3)6.3H2O |
| (Pyrosmalite) | (Fe,Mn)8(OH,Cl)4(SiO3)6.3H2O |
| Schallerite | Mn8(OH)1.2.(As2O5)7.(SiO3)6.3H2O |
| Ferroschallerite | (Mn,Fe,Zn)8(OH) (As2O5)0.85(SiO3)6.3H2O |
| Mcgovernite | (?)21(Mn,Mg,Zn)O.(As2O3)0.5.As2O5.3SiO2.10H2O |
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© by Herb Yeates 1997-2001.
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This
page created: January 12, 2001 6:18 PM
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