Locality: S. Percy Peak, Stratford, NH
Specimen Size: 4.2 cm specimen. Zoom view shows a pair of zoned 9 mm zinnwaldite crystals.
Field Collected: Phil Partington - early 1990's
Catalog No.: 1949
Notes: Gift from Bob Wilken. Bob repatriated this specimen from Arizona on a 2015 trip to the southwest.
Locality: Water Pocket, Blackberry Crossing, Albany, NH
Specimen Size: 1.1 cm hexagonal, zoned, Zinnwaldite crystal
Field Collected: Peter Samuelson
Catalog No.: 1512
Notes: My notes record that an analysis of Water Pocket zinnwaldite was done by Dr. Eugene Foord of the USGS. Many of Peter's specimens were acquired by Harvard University. An auction of excess Harvard specimens, including Water Pocket zinnwaldite, occurred at the October 2005 Capital Club show at Sunapee.
Art Smith had an Excalibur analysis (Oct. 2002) done on a Moose Pocket (nearby) zinnwaldite which is reproduced here.
Locality: Water Pocket, Blackberry Crossing, Albany, NH
Specimen Size: 2.7 cm specimen with embedded zinnwaldite crystals
Field Collected: Tom Mortimer
Catalog No.: 2061
Notes: Specimen has zinnwaldite prism sections to 2 cm with cleavage terminations embedded in feldspar-quartz.
An EDS analysis (BC222 - Aug 2017) done on a polished grain from this specimen indicated almost 8 atomic % Fe, suggesting the siderophyllite species of the zinnwaldite group. However the atomic % ratios of K:Fe:Al of 1:0.4:1 indicated by this analysis of are quite different than those given by webmineral for siderophyllite of about 1:2:3. Note, however, the marked similarity of plots between this BC EDS and the Excalibur EDS above. The unlabeled BC122 EDS peak between the unlabeled carbon peak (277 eV) and the oxygen peak is likely a titanium La peak. There may be a bit of fluorine in the "noise" of the Fe just above the oxygen peak.
The Zinnwaldite group has end members: (mindat.org formulae)
Siderophyllite KFe2Al(Al2Si2O10)(OH)2
Polylithionite KLi2Al(Si4O10)(F,OH)2
Siderophyllite has iron, polylithonite does not. Deer, Howie and Zussman in Introduction to Rock Forming Minerals state (in summary) that the number of ions in the Y sites (includes Al and Fe) is "often considerably less than the theoretical value."
The lower photo illustrates the easy fusibility of this mica, much more easily than biotite-annite.
[tm] I cataloged this as siderophyllite.
[fd]Fred Davis obtained some XRF data on this WP zinnwaldite on 11/29/17. His remark was:
"The zinnwaldite has a nice Rb peak, something I've seen with other New England mica specimens I've examined.
Locality: Water Pocket, Blackberry Crossing, Albany, NH
Specimen Size: 6 cm specimen with embedded 4 cm zinnwaldite crystal
Field Collected: Tom Mortimer
Catalog No.: 2047
Notes: Specimen illustrates size of larger embedded zinnwaldite crystals at the Water Pocket.
Locality: Water Pocket, Blackberry Crossing, Albany, NH
Specimen Size: 2 mm box-work zinnwaldite crystal
Field Collected: Tom Mortimer
Catalog No.: NC
Notes:
Locality: Water Pocket, Blackberry Crossing, Albany, NH
Specimen Size: 2.8 cm x 0.9 cm thick zinnwaldite crystal
Field Collected: Tom Mortimer
Catalog No.: 2065
Notes: Prism surfaces indicate this zinnwaldite crystal formed within an open pocket area.
Locality: Water Pocket, Blackberry Crossing, Albany, NH
Specimen Size: 7 cm specimen with zinnwaldite crystals on microcline & albite. A specimen from the pocket wall.
Field Collected: Uncertain
Catalog No.: 1515
Notes: Acquired from Micromounters of New England give-away table, 2006. Perhaps collected by Bob Janules or Gene Bearss. A few tiny zircons are present. No pyrochlore, or other micros are on this specimen.