Larsenite



Larsenite is a zinc lead silicate mineral. The extant analyses (Dunn, 1985b) conform closely to the theoretical composition. There is little solid solution of other cations in larsenite.
Larsenite was originally described by Palache et al. (1928a, 1928b) from the Franklin Mine. The formula and symmetry had suggested a relation to the olivines, but this was disproven by Layman (1957), who provided accurate cell parameters. Larsenite was synthesized by Ito and Frondel (1967) and Ito (1968). It is among the rarest of the lead silicates from Franklin.
The crystal structure was described by Prewitt et al. (1966, 1967). The structure is composed of a network of corner-linked silicon tetrahedra and zinc tetrahedra and three-sided and distorted four-sided lead pyramids.
Larsenite occurs as colorless, lustrous, commonly acicular prismatic crystals up to several mm in length; the morphology was given in detail by Palache (1935), and the hemimorphic habit was described by Yeates (1991). Thin, platy crystals were observed in one anomalous association with ganomalite and barysilite.
Larsenite aggregates may be white; cleavage is good; the luster is vitreous to adamantine; and the density is 5.90 g/cm3. There is no discernible fluorescence in ultraviolet. Larsenite is distinguished easily from willemite by its crystal habit and lack of fluorescence; the association with altered esperite is helpful as well.
Larsenite was found in superb crystals, but only in a few secondary vein occurrences in the Franklin mine. Although first found in 1928 on the picking table, the one documented occurrence was 20 feet above the 400 level, in top slice 1080 (Palache, 1935). Larsenite is restricted to vein occurrences and forms by direct alteration of primary esperite, which is associated with willemite, franklinite, hardystonite, and calcite. The secondary alteration minerals of this assemblage include larsenite, clinohedrite, hodgkinsonite, and rarely a light-blue-fluorescing mixture of willemite and hodgkinsonite. Ganomalite and barysilite were observed on but one specimen. Valid specimens are rare and prized. (Dunn, 1995)


 Location Found: Franklin (Type Locality)
     
 
 Year Discovered: 1928
     
 Formula: PbZnSiO4
 Essential Elements: Lead, Oxygen, Silicon, Zinc
 All Elements in Formula: Lead, Oxygen, Silicon, Zinc
     
 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   Larsenite

     
 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.381

Frondel, Clifford (1972). The minerals of Franklin and Sterling Hill, a checklist. NY.: John Willey & Sons. p.64


The Picking Table References
 PT Issue and PageDescription / Comment
View IssueV. 33, No. 1 - Spring 1992, pg. 21The Lead Silicate Minerals of Franklin, New Jersey: an SEM Survey, Herb Yeates, Larsenite
View IssueV. 28, No. 1 - Spring 1987, pg. 23Mineral Notes Research Reports, The Esperite Assemblage, Larsenite
View IssueV. 10, No. 1 - February 1969, pg. 12Additional Mineral Notes - Larsenite (Short Note)
View IssueV. 9, No. 1 - February 1968, pg. 6Mineralogical Data - Barysilite and Larsenite
View IssueV. 9, No. 1 - February 1968, pg. 14The Exclusive Minerals of Franklin/Ogdensburg, N.J. (as of January 1968) by Frank Z. Edwards - Larsenite
View IssueV. 7, No. 2 - August 1966, pg. 2Larsenite
     
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