Pumpellyite-(Mg), a calcium magnesium aluminum silicate hydroxide hydrate mineral, is rare at Franklin and unknown from Sterling Hill. Pseudomorphs after feldspar crystals, described by Roepper (1876), were reported by Palache (1935, pp. 60-61) to be a mixture, chiefly zoisite, but including epidote, talc, and a possible feldspar. Re-examination of such well-described crystals in the National Museum found them to be composed of impure pumpellyite-(Mg) (Dunn, 1979c). The crystals have 2.8 wt. % MgO and 1.7 wt. % FeO and are thus the Mg-dominant member of the pumpellyite series. These pseudomorphic crystals were reported to come from what is now known as the Franklin Marble, on Mine Hill. No other mention of pumpellyite or zoisite has been published. (Dunn, 1995)

 Location Found: Franklin
 Formula: Ca2MgAl2(Si2O7)(SiO4)(OH)2 · H2O
 Essential Elements: Aluminum, Calcium, Hydrogen, Magnesium, Oxygen, Silicon
 All Elements in Formula: Aluminum, Calcium, Hydrogen, Magnesium, Oxygen, Silicon
 IMA Status: Approved
 To find out more about this mineral at minDat's website, follow this link   Pumpellyite-(Mg)

Dunn, Pete J. (1995). Franklin and Sterling Hill New Jersey: the world's most magnificent mineral deposits. Franklin, NJ.: The Franklin-Ogdensburg Mineralogical Society. p.419

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