Locality: Chickering Mine, Walpole, NH
Specimen Size: 0.4 mm radial cone of greenish frondelite.
Field Collected: Tom Mortimer (2010)
Catalog No.:
Notes:
Locality: Palermo #1 Mine, Pod #3, N. Groton, NH
Specimen Size: 8 mm field of view top photo. 2 mm field of view, second photo.
Field Collected: Forrest Fogg. Passed along to tm by Gordon Jackson.
Catalog No.: u2205
Notes: Green, tufty, radial balls, of frondelite on hummocks of mitridatite. Frondelite confirmed by polished grain EDS analyses (BC22 - set 19). Chemistry from analysis: Mn1.17Fe4P3.96O22 , normalized for 4 Fe.
Frondelite chemistry is : Mn2+Fe43+(PO4)3(OH)5 .
Frondelite is listed for the Palermo #1 Mine in Whitmore & Lawrence's book The Pegmatite Mines Known as Palermo, but no illustration is included.
In some areas of the specimen, the frondelite appears as scaly masses, third photo.
The fourth view shows the overall 3.5 cm specimen. Zones of frondelite are present on both sides of the specimen.
Fifth photo is attempt to capture some small individual crystal groups.
Whitmore & Lawrence's book lists frondelite for pods #4 and #7, but not for Pod #3.
The label that came with the specimen simply said: "Dark green on mitridatite."
Locality: Chickering Mine, Walpole, NH
Specimen Size: 5 mm field of view. Micro-crystaline frondelite
Field Collected: Tom Mortimer
Catalog No.: u2316
Notes: The rockbridgeite-frondelite series presents substantial difficulties for the amateur mineral collector. Ignoring oxidation states, end member frondelite is MnFe4(PO4)3(OH)5 and
end member rockbridgeite is Fe5(PO4)3(OH)5. Dana's System of Mineralogy, seventh edition, provides analyses that indicate ferroan frondelite and manganoan rockbridgeite exist, blurring species definitions. A frondelite formula including oxidation states is given as (Mn2+,Fe2+)Fe3+4(PO4)3(OH)5. Dana continues, "Divalent manganese and iron [tm, the Mn2+ & Fe2+ in the formula] substitute mutually and probably a complete series extends between the manganese and iron end-members.The names frondelite and rockbridgeite are applied to the halves of the series with Mn2+ > Fe2+ and Fe2+ > Mn2+ respectively."
A Dec. 2019 EDS analysis (BC368A) suggested this Chickering sample is frondelite, although the computed chemistry is not an optimal fit.
An APFU normalized for 3 P yields Mn0.49Fe3.13P3O13.
An APFU normalized for Mn + Fe = 5 yields Mn0.68Fe4.3P4.1O17.9. (The P is high). With some "leap of faith", if we assume four of the 4.3 Fe are Fe3+ and the remaining 0.3 Fe is 2+ , Then we have (Mn2+0.68,Fe2+0.3)Fe3+4P4.1O17.9 . This would fit the Dana frondelite definition with Mn2+ > Fe2+.