Roeblingite is a calcium lead sulfate silicate hydroxide hydrate mineral. Franklin samples have small amounts of Sr, presumably in substitution for Ca. The matter of Penfield and Foote's (1897) report of sulfite in roeblingite was addressed by all subsequent investigators; it is certain that the sulfur is present as sulfate. The nature of the H2O content was settled by Braithwaite (1985) and Moore and Shen (1984).
Roeblingite was first described as a sulfite-bearing mineral by Penfield and Foote (1897). The sulfite was determined to be sulfate by Blix (1931), and Foit (1966) provided unit-cell and powder data. New analyses were provided and the formula was revised by Dunn et al. (1982a). Dunn (1985b) provided additional data and information in a review of the lead silicates at Franklin.
Moore and Shen (1984) determined the crystal structure of roeblingite using Langban material. They found the large cations (Pb and Ca) to be between sheets of composition [Mn(Si3O9)2] and that the silicate radicals have relations to those of margarosanite.
Roeblingite occurs as nodules of interlocking prismatic crystals. These nodules, of roughly rounded shape, are up to 15 cm in diameter, but most are small. No euhedral crystals have been noted. Roeblingite is white, opaque to semi-opaque, sometimes semitransparent, with dull luster; fractured surfaces resemble broken surfaces of porcelain. The density is 3.50 g/cm3. Roeblingite is fluorescent in shortwave ultraviolet with a medium pinkish-red color.
Some massive white aggregates of mixtures of finely-divided sussexite and rhodochrosite resemble roeblingite. Although Franklin roeblingite resembles bakerite, it does not resemble the extremely sparse bakerite reported from Franklin.
Roeblingite was reported by Penfield and Foote (1897) as nodular masses from the 1000 foot level of the Parker Mine in Franklin. Palache (1935) said that Frank Nason noted it near the contacts of marble and pegmatite. Most material has been found on the dumps, and the bulk of it occurs in nodular form.
The majority of these nodules occur within brownish, fine-grained aggregates containing varying amounts of ganophyllite, manganaxinite, andradite, xonotlite, hancockite, prehnite, willemite, hardystonite, clinohedrite, and barite. The nodules' occurrence as irregular aggregates in manganaxinite is noteworthy. A subsequent report (Foote, 1898) was of roeblingite with lead from the 800 foot level.
Roeblingite is also known to occur in veins, where is it occurs with bright green willemite and coarsely-crystallized black hendricksite. At least one occurrence is in altered franklinite/willemite ore. One coarsely-crystallized assemblage yielded a number of spectacular specimens, one of which permitted detailed observation of the sequence of formation of the well-crystallized minerals associated with roeblingite. This description was given by Dunn (1983a) in the description of charlesite. The only published description of an in-situ occurrence of roeblingite was given by Hurlbut and Baum (1960). There has been no detailed study of the possible alteration products of roeblingite. A great many altered specimens are in the collections at Harvard University. The white powdery alteration is charlesite in part.

 Location Found: Franklin (Type Locality)
 Year Discovered: 1897
 Formula: Pb2Ca6Mn2+(Si3O9)2(SO4)2(OH)2 · 4H2O
 Essential Elements: Calcium, Hydrogen, Lead, Manganese, Oxygen, Silicon, Sulfur
 All Elements in Formula: Calcium, Hydrogen, Lead, Manganese, Oxygen, Silicon, Sulfur
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
Fluorescent Mineral Properties

 Shortwave UV light: Moderately bright to weak red
 Mid wave UV light: Weak red
 Longwave UV light: Weak red
 Additional Information: Brief red-orange phosphorescence at shortwave; phosphoresces weakly at other wavelengths
 To find out more about this mineral at minDat's website, follow this link   Roeblingite

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.503

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.74

The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 58, No. 1 - Spring 2017, pg. 16Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Roeblingite
View IssueV. 52, No. 1 - Spring 2011, pg. 21Roeblingite - A Cautionary Tale
View IssueV. 45, No. 1 - Spring 2004, pg. 13The Art of Fluorescent Mineral Photography, With Special Attention to the Minerals of Franklin and Sterling Hill Photographing the More Popular Franklin and Sterling Hill Fluorescent Minerals - Roeblingite
View IssueV. 39, No. 2 - Fall 1998, pg. 13Roeblingite and the "Parker Shaft Minerals"
View IssueV. 33, No. 2 - Fall 1992, pg. 11The Check List of Franklin-Sterling Hill Fluorescent Minerals - Roeblingite (Fluorescent Info)
View IssueV. 33, No. 1 - Spring 1992, pg. 22The Lead Silicate Minerals of Franklin, New Jersey: an SEM Survey, Herb Yeates, Roeblingite
View IssueV. 28, No. 2 - Fall 1987, pg. 15Research Reports, Roeblingite
View IssueV. 28, No. 1 - Spring 1987, pg. 25Mineral Notes Research Reports, The Roeblingite Assemblage
View IssueV. 9, No. 1 - February 1968, pg. 16The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Roeblingite (Short Note)
View IssueV. 8, No. 1 - February 1967, pg. 7Roeblingite

Roeblingite, clinohedrite, ganophyllite, willemite crystals and hancockite from Franklin, NJ
Roeblingite (porcelain white), clinohedrite (white), ganophyllite (gold), willemite crystals (gemmy green) and hancockite (reddish brown) from Franklin, NJ. 4 1/4" x 3 1/8" x 1 1/4". From the collection of, and photo by Robert A. Boymistruk.

All content including, but not limited to, mineral images, maps, graphics, and text on the Franklin-Ogdensburg Mineralogical Society, Inc. (FOMS) website is licensed under a
Creative Commons Attribution-NonCommercial 4.0 International License.
Creative Commons License