FLUORITE

Fluorite was first reported, purportedly from Franklin, by Bruce (1810b), but the occurrence was actually in Hamburg, north of the ore deposits and the presently defined "Franklin-Sterling Hill Area". However, fluorite was reported as "fluate of lime" in many of the reports of the 1820's and as ittro cerite by Gibbs (1823), spelled yttrocerite by Palache (1935).
Local fluorite occurs in masses, as interstitial grains in granular aggregates and as fine, small crystals in vein assemblages. Fiveling twins, similar to that of hetaerolite illustrated by Palache (1935) are rare.
Flow textures are occasionally evident; rounded aggregates are typical, especially where associated with calcite. It is found in red, pink, gray, brown, violet, and other colors; violet and pink are the most common. Some fluorite is violet at the contacts with nickel arsenides. Cleavage is perfect and the density is 3.19 g/cm³. Fluorite is readily distinguished by its cleavage.
Colorless Franklin fluorite has been shown to be thermoluminescent and triboluminescent (Wick, 1937), and brilliant yellow thermoluminscence and white triboluminescence have been reported by Northup and Lee (1940). Colored material is known to fade on exposure to sunlight. Fluorite from the orebodies is largely fluorescent in ultraviolet; that found in the Franklin Marble is commonly non-fluorescent. Where evident, the fluorescence is green to bluish green in longwave and shortwave ultraviolet and rarely vivid violet, stronger in longwave. Some material, when freshly obtained, is phosphorescent in response to incandescent light; see Bostwick (1982). Some orange-brown material which exhibits a bluish-green fluorescence is visible-light-sensitive and the fluorescence diminishes in quality after the specimen has been exposed to visible light for any appreciable time (R. C. Bostwick, personal communication). Additional observations of responses to ultraviolet were given by Millson and Millson (1950) and Jones (1961).
Few chemical data have been published since the analysis given by Palache (1935), except for trace element studies of Sterling Hill fluorite by Buis (1983). She reported that all specimens studied were enriched in Mn, Zn, and Fe and that yttrium was a minor component, confirming the earlier finding of Humphreys (1904). Franklin fluorite was reported to host the rare-earths Dy and Sm (Wicks, 1937); Pb, Sn, Mn, Mg, and Fe were reported by Northup and Lee (1940).
Fluorite occurs in the two orebodies and in the Franklin Marble. At Franklin, massive material is locally common, especially in the Trotter Shaft area, and as an occasional intergranular constituent of the franklinite-willemite ore. Fine crystals are found in some uncommon vein assemblages but, in general, are rare here, unlike at many other ore deposits. Fluorite is associated with many minerals, most commonly with calcite, pyrite, dolomite, sphalerite, and quartz, and also with willemite, titanite, rhodonite, phlogopite, scapolite, rhodochrosite, and others.
Koenig (1890) reported fluorite associated with the rare nickel arsenide assemblage at Franklin. Fluorite is also known as fine crystals in the Buckwheat Dolomite (Peters et al., 1983). Fluorite is also present as druses, late-stage crystals in veins, and breccia cements; an especially notable breccia consists of yellow willemite prisms up to 6 cm in length cemented by colorless fluorite. Additionally, fluorite is an accessory mineral in many associations.
At Sterling Hill, fluorite may have been less common, except in the sulfide veins. Fine crystals were found associated with brown manganaxinite, epidote, and actinolite and separately as colorless dodecahedra associated with chlorophoenicite, rhodochrosite, and allactite. It is found sporadically in small amounts. Buis (1983) examined rare-earth elemental ratios in a significant fluorite band surrounding the black-willemite zone at Sterling Hill and suggested it may have formed in part hydrothermally.
Fluorite is common in the Franklin Marble, especially in fractures, but has not been studied in detail. Occurrences are sporadic, and many are in cavities; well-formed 1 cm violet crystals have been found. Fluorite also is found as a marker-bed in the Kittatinny Limestone. (Dunn, 1995)

Location Found:

Franklin and Ogdensburg

Year Discovered:

1529

Formula:

CaF₂

Essential Elements:

Calcium, Fluorine

All Elements in Formula:

Calcium, Fluorine

IMA Status:

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

Fluorescent Mineral Properties

Shortwave UV light:

White, pale yellow, greenish-yellow, blue-green, green, and blue-violet, variety chlorophane moderately bright blue-green

Mid wave UV light:

White, pale yellow, greenish-yellow, blue-green, green, and blue-violet, variety chlorophane moderately bright blue-green

Longwave UV light:

White, pale yellow, greenish-yellow, blue-green, green, and blue-violet, variety chlorophane moderately bright blue-green

Additional Information:

Chlorophane rapidly loses its fluorescence and phosphorescence (moderately bright blue-green) on exposure to light. Occasionally fluorescence color changes with UV wavelength.

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

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.607

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.56

The Picking Table References

	PT Issue and Page	Description / Comment
View Issue	V. 57, No. 2 - Fall 2016, pg. 18	Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Fluorite
View Issue	V. 45, No. 1 - Spring 2004, pg. 11	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 - Fluorite
View Issue	V. 43, No. 1 - Spring 2002, pg. 16	Yellow-Fluorescing Fluorite And Cuspidine From the Franklin Mine, Franklin, New Jersey John Cianciulli, Curator
View Issue	V. 33, No. 2 - Fall 1992, pg. 10	The Check List of Franklin-Sterling Hill Fluorescent Minerals - Fluorite (Fluorescent Info)
View Issue	V. 30, No. 1 - Spring 1989, pg. 8	The Epidote-Pyroxene-Fluorapophyllite Assemblage in the Franklin Mine at Franklin, New Jersey, Philip P. Betancourt, Fluorite (small description)
View Issue	V. 27 No. 2 - Fall 1986, pg. 6	Minerals of the Franklin Quarry, Philip P. Betancourt, Fluorite
View Issue	V. 24 No. 2 - Fall 1983, pg. 13	Minerals of the Buckwheat Dolomite Franklin, New Jersey, Fluorite (small description)
View Issue	V. 24, No. 1 - Spring 1983, pg. 5	Recent Mineral Occurrences at Sterling Hill, Stephen B. Sanford, Fluorite
View Issue	V. 18, No. 2 - September 1977, pg. 13	The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Fluorite
View Issue	V. 13, No. 2 - August 1972, pg. 12	The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Fluorite (Fluorescent Info)
View Issue	V. 7, No. 2 - August 1966, pg. 8	The Minerals of Sterling Hill 1962-65 by Frank Z. Edwards - Fluorite

Images


Fluorite (clear, orange and purple), calcite and garnet from Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.		Fluorite, calcite and garnet from Franklin, NJ under longwave UV light. The fluorite fluoresces blue and lavender, calcite red-orange, the garnet is non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.

Fluorite, calcite and garnet from Franklin, NJ under shortwave UV light. The fluorite fluoresces gray-blue and lavender, calcite orange-red and the garnet is non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


Fluorite (red-brown), calcite (white), willemite (white to pink) and franklinite (black) from the Parker Shaft, Franklin, NJ. From the collection of, and photo by Robert A. Boymistruk.		Fluorite, calcite, willemite and franklinite from the Parker Shaft, Franklin, NJ under shortwave UV light. The fluorite fluoresces gray, willemite green and the calcite red-orange, franklinite is non-fluorescent. From the collection of, and photo by Robert A. Boymistruk.


Fluorite (light purple, light brown and clear), calcite (white) and franklinite (black) from Franklin, NJ. 2 3/4" x 2". From the collection of, and photo by Robert A. Boymistruk.		Fluorite, calcite and franklinite from Franklin, NJ under shortwave UV light. The fluorite fluoresces gray-blue to lavender, calcite orange-red, and the franklinite is non-fluorescent. 2 3/4" x 2". From the collection of, and photo by Robert A. Boymistruk.


Fluorite (brown to sherry-red var. "chlorophane", clear), with minor calcite, willemite and franklinite (black) from the Buckwheat dump Franklin, NJ. 4 1/4" x 2 1/4". Photo by WP.		Fluorite "chlorophane", with minor franklinite, willemite and calcite, from the Buckwheat dump Franklin, NJ under longwave UV light. The chlorophane variety fluoresces weak blue, teal and the clear portions of the fluorite blue-violet, the calcite, willemite and franklinite are non-fluorescent. 4 1/4" x 2 1/4". Photo by WP.

Fluorite "chlorophane", with minor franklinite, willemite and calcite, from the Buckwheat dump Franklin, NJ under shortwave UV light. The chlorophane variety fluoresces teal, calcite orange and willemite green, the clear portions of the fluorite and franklinite are non-fluorescent. 4 1/4" x 2 1/4". Photo by WP.