GOEDKENITE AND PALERMOITE: PALERMO #!

If opportunity doesn't knock, build a door.

    Milton Berle

I spent a fair amount of time pondering over how to write a posting on a couple of very unfamiliar minerals. Especially writing about minerals that are so tiny, good photomicrographs (with my equipment) are tough to produce. But I wanted to remove them from my “to do” list. So, with no opportunity presenting itself I built a door, knocked, and waded into the swamp. Welcome to Mike’s cabinet of very unfamiliar minerals!

One of the more famous pegmatite mines in the eastern U.S. is the Palermo #1 Mine near North Groton, Grafton County, New Hampshire, one of the several pegmatites emplaced along the western part of the State. These pegmatite bodies are located in the Acadian Orogenic Belt, a tectonic area that represents the Devonian (~420Ma --~360 Ma) uplift of mountains in the northern section of the Appalachian Orogen, around southern Virginia to Newfoundland. This uplift was the result of plate movement as a microcontinent named Avalonia (parts of Europe) was banging against Laurentia (proto–North America) and being accreted (the terrane was sticking to Laurentia) while the proto-Atlantic Ocean was being subducted under the Laurentian continental plate. Of course, the orogenic event was much more complex than this explanation!

The Grafton pegmatites are a hotbed for finding phosphate minerals, including the Palermo #1 pegmatite where something like 159 minerals with 15 Types, many of them phosphates, have been identified (MinDat.org). The pegmatites within the area of Palermo mine #1 (and mines #2, and #3) are quite complex but have as their primary phosphates triphylite (Li, Fe) AND/OR lithiophylite (Li, Mn), and montebrasite (Li, Al) AND/OR ambygonite (Li, Al, F). These primary minerals then interacted with post-magmatic aqueous fluids to produce several tens of secondary phosphate minerals (Nizamoff, 2006) .

Two of these rare, late-stage secondary hydrothermal minerals from a complex granite pegmatite exposed at Palermo #1 are goedkenite Sr₂Al(PO₄)₂(OH) and palermoite (Li,Na)₂(Sr,Ca)Al₄(PO₄)₄(OH)_4. Goedkenite, a strontium aluminum hydrated phosphate is the lesser known of the two although they are close allies at the Type Locality as goedkenite was originally found as tiny crystals growing epitaxally and perpendicularly on palermoite crystals (Moore and others, 1975). Goedkenite crystals are prismatic, transparent, colorless, or pale yellow, sub-vitreous, and usually less than 1 mm in length. They have a white streak and a measured hardness of ~5.0 (Mohs). Goedkenite is only known from a couple of areas, the Palermo #1 in New Hampshire, and the Lupka Quarry in Slovakia.

Two larger crystals of palermoite (a V) with microscopic epitaxial crystals of goedkenite.

Two isolated transparent crystals of goedkenite (right center).

Submillimeter transparent crystal of goedkenite (close to center of photo)..

Splintery clusters of palermoite crystals

Submillimeter transparent, prismatic, epitaxial crystals of goedkenite "sprouting" from larger palermoite crystals.

My guess is there is a second growth of epitaxial crystals of goedkenite. The larger palermoite crystal is out of focus on the bottom.

Palermoite, is the better known of the two friends due to its name being derived from the Palermo pegmatite (Mrose, 1953). It is a lithium strontium hydrated phosphate [(Li,Na)₂(Sr,Ca)Al₄(PO₄)₄(OH)₄], and like goedkenite, is quite rare and only known from three localities, the Type Locality, the Nanping pegmatite field in China, and Toirano in Italy (as noted by MinDat).

Crystals are usually prismatic and splintery, transparent, colorless to white, vitreous, and occur as individuals or clusters of crystals. The mineral has a white streak and a measured hardness of ~5.5 (Mohs). Palermoite crystals are longer that goedkenite but still only a few mm in length (or less).

Unknown. Nice crystal.

 

Unknown.

Unknown green mineral.

Unknown. Maybe phosphosiderite?

Unknown. Could it be foggite??

Nizamoff and others (2022) described the Palermo #1 pegmatite as “a beryl-phosphate pegmatite member of the LCT (lithium,-cesium,- or tantalum-enriched) family and is enriched in phosphorus.

My specimen is a micromount (~1 cm x ~1cm) collected and mounted by John Reiner and then acquired by Art Smith in 1981. Reiner’s (1909-1995) memorial is in Rocks and Minerals, vol. 71, no. 2.

The micromount ~1 cm X ~1 cm. Full of crystals.

                                     REFERENCES CITED

Mrose, M.E.,1953, Palermoite and goyazite, two strontium minerals from the Palermo mine, North Groton, New Hampshire. (Abstract from the 33rd annual meeting of the Mineralogical Society of America): American Mineralogist: vol. 38.

Moore, P.B., Irving, A.J., Kampf, A.R., 1975, Foggite, CaAl(OH)2(H2O)[PO4]; goedkenite, (Sr,Ca)2Al(OH)[PO4]2; and samuelsonite, (Ca,Ba)Fe22+Mn22+Ca8Al2(OH)2[PO4]10. Three new species from the Palermo No. 1 pegmatite, North Groton, New Hampshire: American Mineralogist vol. 60.

Nizamoff, J., 2006, The Mineralogy, Geochemistry and Phosphate Paragenesis of the Palermo #2 Pegmatite, North Groton, New Hampshire: University of New Orleans Theses and Dissertations. 398.

Nizamoff, J.W., R,W. Whitmore, and M.I. Jacobson, 2022, The Where of Mineral Names: Palermoite, Palermo No. 1 Mine, North Groton, Grafton County, New Hampshire: Rocks and Minerals, vol.97, no.3.