Crystal System: Orthorhombic
Status of Occurrence: Confirmed Occurrence - 1st UK recording
Chemical Composition: Manganese magnesium silicate hydroxide
Chemical Formula: (Mn,Mg)7(SiO4)3(OH)2
Method(s) of Verification: Harlech Dome - EMPA (Bennett, 1987a, analysis 12457).
- Metamorphic: skarn mineralization
- Metamorphic: low-grade
Introduction: a rare manganese magnesium silicate mineral belonging to the humite group. It is typically found in manganese deposits metamorphosed under amphibolite facies conditions and as a late-stage skarn mineral (Anthony et al., 1995).
Occurrence in Wales: Bennett (1987a) reported manganhumite from the Cambrian manganese deposits of the Harlech Dome area of Gwynedd. This appears to be the first recording of this mineral in the British Isles.
- Llŷn Dywarchen, Moel Ysgyfarnogod, Gwynedd: Bennett (1987a) reported the presence of rare, orange-yellow Mn-humite associated with barite in a microconcretion and in adjacent carbonate-rich, red laminated ore in the manganese ore bed of the Hafotty Formation of Cambrian age from Llŷn Dywarchen near Moel Ysgyfarnogod.
- Anthony J., Bideaux R., Bladh K. & Nichols M., 1995. Handbook of Mineralogy, vol. 2 (parts 2/1 and 2/2), Silica, Silicates
- Bennett, M.A., 1987a. The Cambrian manganese deposits of North Wales. Unpublished Ph.D. thesis, University of Leeds.