Humite (mineral group)
The humite group[1] is a group of nesosilicates with the general formula A
n(SiO
4)
m(F,OH)
2.
When A is predominantly magnesium we have the humite subgroup:
- norbergite, Mg
3(SiO
4)(F,OH)
2 - chondrodite, (Mg,Fe,Ti)
5(SiO
4)
2(F,OH,O)
2 - humite, (Mg,Fe)
7(SiO
4)
3(F,OH)
2 - clinohumite, (Mg,Fe)
9(SiO
4)
4(F,OH)
2
The manganese-humite subgroup has members
- alleghanyite, (Mn2+)
5(SiO
4)
2(OH,F)
2 - manganhumite, (Mn,Mg)
7(SiO
4)
3(OH)
2 - sonolite, Mn
9(SiO
4)
4(F,OH)
2
and the leucophoenicite subgroup has members
- ribbeite, Mn
5(SiO
4)
2(OH)
2 - leucophoenicite, (Mn,Ca,Mg,Zn)(SiO
4)
3(OH)
2 - jerrygibbsite (Mn,Zn)
9(SiO
4)
4(OH)
2
Chondrodite is the most common member of the humite group. It may contain Ti up to 9.6% TiO
2. Chondrodite from Sterling Hill Mine and Franklin Mine contains zinc to 11.5% ZnO and Mn to 36% MnO, and grades to alleghanyite.
The humite minerals commonly alter to serpentine or Mg-rich chlorite and dissolve by weathering, leaving iron oxide residues.[2]
References
- Gaines et al (1997) Dana's New Mineralogy Eighth Edition, Wiley
- Phillips, W R and Griffen, D T (1981) Optical Mineralogy, pages 142 to 144
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