MARGAROSANITE

Margarosanite is a calcium lead silicate mineral; Mn and Zn proxy for Ca in small amounts (Dunn, 1985b). Most samples conform to the ideal composition, and solid solution is limited.
Margarosanite was partially described from Franklin by Penfield and Warren (1899) and was subsequently described in full and named by Ford and Bradley (1916). New optical and X-ray data were provided by Armstrong (1963) using Franklin material. Glasser and Glasser (1964) provided additional crystallographic data and showed that margarosanite is related to artificial Ca₂BaSi₃O₉. Margarosanite was synthesized by Ito (1968).
The crystal structure of margarosanite was solved by Freed and Peacor (1969) who noted relations to walstromite, benitoite, and wadeite. They reported the structure to have layers of tetrahedra alternating with layers of calcium polyhedra between layers of close-packed oxygen atoms. They further noted that the tetrahedral sites form three-membered rings which are linked to a Ca polyhedral chain, along which Pb and additional Ca atoms, which are ordered, alternate.
Margarosanite occurs as platy masses, composed of lamellae up to 4 cm, but commonly smaller, commonly foliate and warped, and sometimes in divergent arrays or sprays. Large clean samples are prized. Margarosanite is colorless to white, but may have an apparent bluish tint. It has a distinctly pearly to vitreous luster and a density of 4.33 g/cm³.
A striking property of Franklin margarosanite is its fluorescence: a strong violet-blue in shortwave ultraviolet. Some specimens may have red to pinkish fluorescence (Miller, 1974). Margarosanite is strongly cathodoluminescent with bright blue color, similar in intensity to that of benitoite. Margarosanite visually resembles the best minehillite and is distinguished from it easily by its indices of refraction and its strong blue fluorescence in ultraviolet.
Margarosanite is one of the more widely distributed minerals of the restricted lead silicate assemblage; nasonite is the only lead silicate which occurs associated with more species. The most commonly associated minerals are manganaxinite, andradite, and microcline. Others are minehillite, bustamite, grossular, prehnite, nasonite, wollastonite, vesuvianite, clinohedrite, willemite, and rarely vesuvianite, to mention only some. The association with minehillite is particularly noteworthy (Dunn et al., 1984a). Perhaps in part due to its strong and lovely fluorescence in ultraviolet, the species has possibly been selectively overcollected relative to the other lead silicates. Some confusion regarding the fluorescence of barylite resulted in many samples of margarosanite in microcline being mislabeled as barylite in the period 1930-1990. (Dunn, 1995)

Location Found:

Franklin (Type Locality)

Year Discovered:

1916

Formula:

Pb(Ca,Mn²⁺)₂(Si₃O₉)

Essential Elements:

Calcium, Lead, Oxygen, Silicon

All Elements in Formula:

Calcium, Lead, Manganese, Oxygen, Silicon

IMA Status:

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"

Fluorescent Mineral Properties

Shortwave UV light:

Bright pale blue, often with red zones, less often with white and pink zones

Mid wave UV light:

Moderately bright red, orange

Longwave UV light:

Weak red, orange

To find out more about this mineral at minDat's website, follow this link Margarosanite

References:

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.499

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.67

The Picking Table References

	PT Issue and Page	Description / Comment
View Issue	V. 58, No. 1 - Spring 2017, pg. 12	Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 2, Richard C. Bostwick - Margarosanite
View Issue	V. 45, No. 1 - Spring 2004, pg. 12	The 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 - Margarosanite
View Issue	V. 33, No. 2 - Fall 1992, pg. 11	The Check List of Franklin-Sterling Hill Fluorescent Minerals - Margarosanite (Fluorescent Info)
View Issue	V. 33, No. 1 - Spring 1992, pg. 22	The Lead Silicate Minerals of Franklin, New Jersey: an SEM Survey, Herb Yeates, Margarosanite
View Issue	V. 28, No. 1 - Spring 1987, pg. 24	Mineral Notes Research Reports, The Margarosanite Assemblage
View Issue	V. 18, No. 2 - September 1977, pg. 15	The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Margarosanite
View Issue	V. 13, No. 2 - August 1972, pg. 12	The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Margarosanite (Fluorescent Info)
View Issue	V. 11, No. 1 - February 1970, pg. 10	Mineral Data - Margarosanite
View Issue	V. 4, No. 2 - August 1963, pg. 10	Margarosanite

Images


Margarosanite, clinohedrite, willemite in feldspar matrix, from Franklin, New Jersey. From the collection of, and photo by JVF.		Margarosanite, clinohedrite, willemite in feldspar matrix, from Franklin, New Jersey, under shortwave UV light. The margarosanite fluoresces blue, clinohedrite orange, and the willemite green. From the collection of, and photo by JVF.


Platy margarosanite on hancockite with minor willemite, franklinite, roeblingite and clinohedrite, from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.		Platy margarosanite on hancockite with minor willemite, franklinite, roeblingite and clinohedrite, from Franklin, NJ under shortwave UV light. The margarosanite fluoresces blue, roeblingite red, clinohedrite orange and the willemite green, the franklinite is non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


Margarosanite on feldspar with andradite and minor willemite from Franklin, NJ. Photo by JVF.		Margarosanite on feldspar with andradite and minor willemite from Franklin, NJ under shortwave UV light. The margarosanite fluoresces blue and the willemite green, the feldspar and andradite are non-fluorescent. Photo by JVF.