Esperite
Current inventory:  0 gems
 

  
Esperite was named in 1965 by Paul Brian Moore and Paul H. Ribbe in honor of Esper Signius Larsen, Jr. (March 14, 1879 - March 8, 1961), petrologist and Professor of Geology at Harvard University, Cambridge, Massachusetts, USA.

Discovered in 1928; IMA status: Valid (IMA approved 1965)

Chemistry

Chemical Formula:

PbCa₃Zn₄(SiO₄)₄

Lead Calcium Zinc Silicate

Molecular Weight:

957.33 gm

Composition:

Calcium

12.56 %

Ca

17.57 %

CaO

Zinc

27.32 %

Zn

34.01 %

ZnO

Silicon

11.73 %

Si

25.11 %

SiO₂

Lead

21.64 %

Pb

23.31 %

PbO

Oxygen

26.74 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/A.03-20

Nickel-Strunz 10th Ed. ID:

9.AB.15

9 : SILICATES (Germanates)

A : Nesosilicates
B : Nesosilicates without additional anions; cations in [4] and greater coordination

Related to:

Isostructural with: Beryllonite, Larsenite

Varieties:

None

Synonyms:

Calcium-Larsenite, IMA1964-027

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

Granular aggregates, massive, to 9 cm

Twinning:

None

Physical Properties

Cleavage:

Distinct on {010} and {100}; poor on {101}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

5.0 - 5.5

Density:

4.28 - 4.42 (g/cm³)

Luminescence:

Fluoresces bright yellow under SW UV (Franklin); dull yellow under LW UV; kelly green cathodoluminescence

Radioactivity:

Not Radioactive

Optical Properties

Color:

White, off-white, pale tan; darkening on exposure to light

Transparency:

Opaque, transparent in small grains

Luster:

Sub-vitreous; dull to slightly greasy

Refractive Index:

1.762 - 1.774  Biaxial ( - ) 

Birefringence:

0.012

Dispersion:

Very Strong

Pleochroism:

None

Occurances

Geological Setting:

Metamorphosed stratiform zinc-iron-manganese orebody.

Common Associations:

Willemite, Zincite, Hardystonite, Glaucochroite, Andradite, Franklinite, Clinohedrite, Leucophoenicite, Larsenite, Copper

Common Impurities:

Fe, Mn, Mg

Type Locality:

Parker Mine (Parker shaft), Franklin Mine, Franklin, Franklin Mining District, Sussex County, New Jersey, USA

Year Discovered:

1928

View mineral photos:

Esperite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Esperite is a rare complex calcium lead zinc silicate mineral that was discovered in 1928 at the Parker shaft of the Franklin Mine, Franklin, Sussex County, New Jersey, USA. It was originally named calcium-Larsenite for its calcium content and relationship to Larsenite (PbZnSiO4). Larsenite was named in 1928 by Charles Palache, Lawson Henry Bauer and Harry Berman to honor Esper Signius Larsen, Jr. (1879 - 1961), petrologist and Professor of Geology at Harvard University, Cambridge, Massachusetts, USA. Calcium-Larsenite was renamed "Esperite" in 1965 by Paul Brian Moore and Paul H. Ribbe also in honor of Esper Larsen, Jr. It was approved by the International Mineralogical Association (IMA) as a valid distinct mineral species in 1965.

Esperite is one of over 350 types of minerals found at Franklin and Sterling Hill, New Jersey. It is also one of about 89 fluorescent minerals found there. Esperite has a white or off-white to pale tan appearance in daylight but is prized for its brilliant yellow to yellow-green fluorescence under shortwave (SW) ultraviolet (UV) light (click on the picture above to see its color under SW-UV light). It is often found in association with other fluorescent minerals such as Calcite, Hardystonite, Willemite, Clinohedrite and non-fluorescent, black Franklinite. Although Esperite is mainly known for its occurrence at Franklin, it is also found as prismatic crystals up to 1 mm in length at the El Dragón Mine, Antonio Quijarro Province, Potosi Department, Bolivia. These are the only two localities known to contain Esperite.
 

  
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