Vesuvianite



Vesuvianite is basically a calcium magnesium aluminum silicate hydroxide mineral; small amounts of other cations are essential, and at Franklin, these can be Fe, Mn, Cu, or Zn. The formula given in the heading is that of Fitzgerald et al. (1986), determined for a blue vesuvianite; the supporting data were modified by Fitzgerald et al. (1992). Four anomalous aspects of the composition of Franklin vesuvianites are the concentrations of copper, beryllium, manganese, and zinc.
The maximum copper content of blue fibrous vesuvianite was found to be 1.85 wt. % CuO by Steiger in Palache (1910), 1.91 wt. % CuO by Fitzgerald et al. (1986), and 2.17 wt. % CuO by Fitzgerald et al. (1992). Numerous analyses by [Dunn] indicate a maximum CuO content of 2.1 wt. %; those of Groat et al. (1992) have values less than this. Some blue crystals (FeO 1.2, MgO 0.9 wt. %) are overgrown by violet rims (FeO 0.8, MgO 2.2 wt. %); this relation remains unstudied.
The beryllium content of Franklin vesuvianite has been the focus of several investigations. It was first reported by Palache and Bauer (1930), who reported 9.2 wt. % BeO in brown prismatic crystals. Hurlbut (1955) reinvestigated this material, using samples of purported "beryllian" vesuvianite provided by Bauer, and gave analyses by Gonyer showing only 1.56 to 3.95 wt. % BeO. However, in the absence of proof to the contrary, one must conclude that Be is not a major constituent of the preponderance of Franklin vesuvianite.
The manganese content of Franklin vesuvianite is quite limited; no specimen among many studied by [Dunn] has more than 4.1 wt. % MnO (total Mn calculated as MnO). The zinc content of local vesuvianite has been examined by Groat et. al. (1992) who reported a maximum of 2.35 wt % ZnO; Fitzgerald et al. (1992) found 4.46 wt. % ZnO.
Sterling Hill vesuvianite has not been analyzed, but it occurs in a typical calcium silicate assemblage and may be of normal composition.
Vesuvianite was first reported from Franklin by Vanuxem and Keating (1822b), but Palache attributed such early reports to mistaken identifications of uvite in marble. Vesuvianite was later described by Penfield (1899) as red crystals in nasonite. Bright blue vesuvianite, first found by Palache in 1905, was subsequently found in abundance in 1922 and was studied by Shannon (1922), who called it cyprine, and by Lewis and Bauer (1922). Palache and Bauer (1930) reported the occurrence of a purported beryllian vesuvianite, Be-vesuvianite; Palache (1935) called this material beryllium vesuvianite. Vesuvianite is found in moderate amounts at Franklin and is perhaps less common at Sterling Hill.
Franklin vesuvianite occurs in a wide variety of habits; it is known in fine crystals and in radiating and fibrous crystal aggregates. The crystals figured by Palache (1935) are among the best and are of simple morphology.
Franklin vesuvianite has much variance in color: it is red, reddish-brown, brown, green, deep bright green, violet, and bright blue; Sterling Hill vesuvianite is greenish brown. The luster is vitreous, cleavage is indistinct, and the density is 3.385 g/cm3 for reddish brown crystals. There is no discernible fluorescence in ultraviolet.
Franklin vesuvianite occurs in a number of assemblages. Most of the preserved specimen material is the blue vesuvianite (cyprine), which is associated with garnet (presumably andradite-grossular), hyalophane, willemite, hardystonite, barite, calcite, mica, and bustamite. This was found in abundance in 1922 near the 850 level, 400 feet south of the Parker Shaft. In this assemblage, vesuvianite varies from blue to green to blue-violet and varies in texture from fine-grained fibrous to coarse-grained fibrous to granular; it also occurs in coarse-grained radial aggregates of prismatic crystals. Mica (presumably phlogopite) is replaced by blue vesuvianite in some specimens, and some caswellite is in part vesuvianite. Green vesuvianite is commonly massive; crystals and fibrous textures were not observed. It is very likely that the preponderance of blue material in local and systematic collections is due to selective retention of these very attractive specimens.
Of substantial significance is the vesuvianite reported to contain Be. This assemblage consists of massive andradite and leucophoenicite, with subhedral crystals of light green willemite, barite, and a very light brown to white unanalyzed apatite-group mineral. Vesuvianite occurs as abundant brown prismatic crystals, as depicted by Palache (1935), which grade into fine-grained material. Gageite occurs as colorless radial sprays of crystals, found most commonly where the silicates contact barite. The assemblage appears to be a breccia.
The Franklin vesuvianite which has the maximum Mn-content is from a simple assemblage consisting largely of massive brown andradite which contains minor amounts of willemite, franklinite, and calcite. Vesuvianite is found as irregular segregations, up to 5 cm, with a dark red color; much of this material is massive, but fine crystals are found at contacts with calcite.
Among the best crystals of Franklin vesuvianite are those which occur as sharp, clear, light brown, 1-2 mm euhedra, together with dull-lustered, nearly black, dark red leucophoenicite, and willemite crystals as a late-stage vein assemblage on a white matrix. This matrix is composed for the most part of white granular grossular (a replacement of an unknown precursor) with minor amounts of willemite and andradite. Vesuvianite occurs on fracture surfaces in this matrix, followed by leucophoenicite and then willemite.
The above Franklin assemblages are but the most notable; vesuvianite also occurs sporadically in a number of other associations, many evident only in one-of-a-kind specimens, and mostly unstudied. These include brown crystals on vein surfaces and brown, green, and red massive material. Of particular interest are the red Mn-bearing vesuvianites and a rare association of vesuvianite with tephroite.
Contrary to the assertion of Leavens (1990), vesuvianite is known from Sterling Hill; the assemblage is unstudied. It occurs as greenish brown, isolated, subhedral, 2-3 mm crystals associated with light brown garnet (presumably grossular), calcite, and diopside, in a typical calcium-silicate vesuvianite assemblage. (Dunn, 1995)


 Location Found: Franklin and Ogdensburg
     
 Mineral Note: Cyprine was a name previously given to any blue variety of vesuvianite
 Year Discovered: 1795
     
 Formula: (Ca,Na,☐)19(Al,Mg,Fe3+)13(☐,B,Al,Fe3+)5(Si2O7)4(SiO4)10(OH,F,O)10
 Essential Elements: Aluminum, Calcium, Hydrogen, Magnesium, Oxygen, Silicon
 All Elements in Formula: Aluminum, Boron, Calcium, Fluorine, Hydrogen, Iron, Magnesium, Oxygen, Silicon, Sodium
     
 IMA Status: Valid - first described prior to 1959 (pre-IMA) - "Grandfathered"
     
     
 To find out more about this mineral at minDat's website, follow this link   Vesuvianite

     
 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.421

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.82


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 19, No. 2 - September 1978, pg. 11The Post Palache Minerals by Frank Z. Edwards - Beryllium Idocrase-Vesuvianite
View IssueV. 11, No. 2 - August 1970, pg. 10Additional Mineral Notes - Idocrase (Vesuvianite) (small article)
     
Images

     
Vesuvianite, with calcite, and hendricksite mica, from Franklin, New Jersey
Vesuvianite (yellow tan), with calcite (white), and hendricksite mica (shiny black), from Franklin, New Jersey. From the collection of and photo by Ken Reynolds.


Cyprine (blue), willemite, calcite, hendricksite mica, from Franklin
Vesuvianite variety Cyprine (blue), with willemite, calcite, and hendricksite mica (shiny black), from Franklin, New Jersey. From the collection of and photo by JVF.


Cyprine (blue), willemite "blue", franklinite, andradite, hendricksite, FranklinCyprine (blue), willemite "blue", franklinite, andradite, hendricksite, Franklin under shortwave UV Light
Vesuvianite variety cyprine (blue), willemite, franklinite, andradite (light brown), and hendricksite mica (shiny black). Photo by JVF.
Vesuvianite variety cyprine, thoroughly mixed with willemite under shortwave UV light, giving the appearance of "blue willemite". Cyprine is non-fluorescent. The calcite fluoresces red and the willemite green. Photo by JVF.


Vesuvianite variety cyprine, willemite, calcite, hendricksite mica and andradite garnet from Franklin, NJVesuvianite variety cyprine, willemite, calcite, hendricksite mica and andradite garnet from Franklin, NJ under longwave UV Light
Vesuvianite variety cyprine (blue), willemite (light green and white), calcite (white), hendricksite mica (shiny black) and andradite garnet (brown) from Franklin, NJ. 6" x 4 1/2". From the collection of Gerry McLoughlin, photo by WP.
Vesuvianite variety cyprine, willemite, calcite, hendricksite mica and andradite garnet from Franklin, NJ under longwave UV light. The willemite fluoresces green and the calcite dark red, the cyprine, mica and garnet are non-fluorescent. 6" x 4 1/2". From the collection of Gerry McLoughlin, photo by WP.
Vesuvianite variety cyprine, willemite, calcite, hendricksite mica and andradite garnet from Franklin, NJ under shortwave UV Light
Vesuvianite variety cyprine, willemite, calcite, hendricksite mica and andradite garnet from Franklin, NJ under shortwave UV light. The willemite fluoresces green and the calcite orange red, the cyprine, mica and garnet are non-fluorescent. The blue cyprine includes exsolution willemite and appears to fluoresce green. 6" x 4 1/2". From the collection of Gerry McLoughlin, photo by WP.







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