ESPERITE

Esperite is a calcium lead zincosilicate mineral, related to beryllonite and trimerite. Ten microprobe analyses were given by Dunn (1985b).The known reliable analyses conform closely to Ca₃PbZn₄(SiO₄)₄, with some limited substitution of Mn and Mg for Zn, and Pb for Ca.
Esperite was originally described and named calcium larsenite by Palache et al. (1928a, 1928b), because it was assumed to be related to larsenite. Restudy by Moore and Ribbe (1965) established its independent status as a zincosilicate; they renamed it esperite. Esperite was synthesized by Ito (1968), and thermal decomposition data were given by Moore and Ribbe (1965). The crystal structure is unsolved.
Esperite is massive, forming fine-grained aggregates, some over 15 cm in diameter. The color is white to light yellow, but most specimens are of dingy appearance; the luster is variable, slightly greasy on fresh surfaces, but dull on exposed surfaces. Cleavage was not observed, but there is a conchoidal fracture, and some masses have a weak foliation, likely stress-induced. The density is 4.42 g/cm³. Esperite fluoresces in ultraviolet, with a strong yellow-green color in shortwave; this is a diagnostic feature. The fluorescence is diminished at contacts with franklinite.
The duration of phosphorescence (33 hours) was noted by Millson and Millson (1950). Esperite has a pale greenish-white thermoluminescence, and its response is the most thermally unstable of all the minerals studied by Northup and Lee (1940). It attained maximum brilliance and then extinguished, at temperatures below those for any other studied mineral.
Esperite is a primary mineral and is moderately widespread at Franklin, but has not been found at Sterling Hill. It was originally found on the 400 foot level of the mine, approximately 1080 feet north of the north side of the Palmer Shaft pillar. It was subsequently found in other parts of the northern end of the orebody, but aside from one occurrence on the 1100 level with glaucochroite, specific locations were not noted.
The common occurrence is of somewhat nodular masses, up to 15 cm, associated with hardystonite, willemite, franklinite and, less commonly, calcite. Associated franklinite is rimmed with willemite in many specimens. Less common associated species are nondescript gray-to-brown glaucochroite and light pink hodgkinsonite, which commonly occurs in minor amounts at the feathery reaction zone where hardystonite is replaced by esperite. The replacement of hardystonite can be complete. An unnamed species occurs within this reaction zone as well (Dunn, 1985b). Ito (1968) noted a Ca-Zn-silicate mineral in this assemblage. (Dunn, 1995)

Location Found:

Franklin (Type Locality)

Year Discovered:

1928

Formula:

PbCa₂Zn₃(SiO₄)₃

Essential Elements:

Calcium, Lead, Oxygen, Silicon, Zinc

All Elements in Formula:

Calcium, Lead, Oxygen, Silicon, Zinc

IMA Status:

Approved 1964

Fluorescent Mineral Properties

Shortwave UV light:

Very bright lemon-yellow

Mid wave UV light:

Weak lemon-yellow

Longwave UV light:

Weak lemon-yellow

Additional Information:

Very weak phosphorescence

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

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.368

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.55

The Picking Table References

	PT Issue and Page	Description / Comment
View Issue	V. 57, No. 2 - Fall 2016, pg. 17	Fluorescent Minerals of Franklin and Sterling Hill, N.J., Part 1, Richard C. Bostwick - Esperite
View Issue	V. 51, No. 2 - Fall 2010, pg. 7	Abstract of the redefinition of Franklin esperite formula and structure.
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 - Esperite
View Issue	V. 43, No. 1 - Spring 2002, pg. 29	In Praise of Esperite Richard C. Bostwick
View Issue	V. 33, No. 2 - Fall 1992, pg. 10	The Check List of Franklin-Sterling Hill Fluorescent Minerals - Esperite (Fluorescent Info)
View Issue	V. 33, No. 1 - Spring 1992, pg. 19	The Lead Silicate Minerals of Franklin, New Jersey: an SEM Survey, Herb Yeates, Esperite
View Issue	V. 28, No. 1 - Spring 1987, pg. 23	Mineral Notes Research Reports, The Esperite Assemblage
View Issue	V. 18, No. 1 - March 1977, pg. 24	The Fluorescent Minerals of Franklin and Sterling Hill, NJ by Richard C. Bostwick - Esperite
View Issue	V. 13, No. 2 - August 1972, pg. 12	The Fluorescent Minerals of Franklin/Ogdensburg Area by Frank Z. Edwards - Esperite (Fluorescent Info)
View Issue	V. 9, No. 1 - February 1968, pg. 12	The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Esperite
View Issue	V. 6, No. 1 - February 1965, pg. 6	Esperite, a Proposed New Name for Calcium-Larsenite

Images


Esperite (white), willemite (light green), franklinite (black) and calcozincite (brown) from Franklin, New Jersey. From the collection of, and photo by, JVF.		Esperite, willemite, franklinite and calcozincite from Franklin, New Jersey under shortwave UV light. The esperite fluoresces yellow, and the willemite green. From the collection of, and photo by, JVF.

Esperite, willemite, franklinite and calcozincite from Franklin, New Jersey under longwave UV light. The esperite fluoresces yellow, and the willemite green. From the collection of, and photo by, JVF.


Esperite (white to beige), calcite (wite to light gray), franklinite (black), hardystonite (white to beige), minor zincite (red-brown) and willemite from Franklin, New Jersey. 4 1/2" x 3 1/2". From the collection of Zack and Ralph Bonard, photo by WP.		Esperite, calcite, franklinite, hardystonite, minor zincite and willemite from Franklin, New Jersey under shortwave UV light. The esperite fluoresces yellow, calcite orange-red, hardystonite violet-blue, willemite green, the zincite and franklinite are non-fluorescent. 4 1/2" x 3 1/2". From the collection of Zack and Ralph Bonard, photo by WP.