Hardystonite
Current inventory:  0 gems
 

  
Hardystonite was named after Hardyston Township, Sussex County, New Jersey, USA, locality of the Franklin orebody prior to incorporation of Franklin Borough in 1913. Hardyston Township surrounds the borough of Franklin today.

Discovered in 1899; IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Ca₂ZnSi₂O₇

Calcium Zinc Silicate

Molecular Weight:

313.71 gm

Composition:

Calcium

25.55 %

Ca

35.75 %

CaO

Zinc

20.84 %

Zn

25.94 %

ZnO

Silicon

17.91 %

Si

38.31 %

SiO₂

Oxygen

35.70 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/C.02-40

Nickel-Strunz 10th Ed. ID:

9.BB.10

9 : SILICATES (Germanates)
B : Sorosilicates
B : Si₂O₇ groups, without non-tetrahedral anions; cations in tetrahedral [4] and greater coordination

Related to:

Melilite Group.

Members of Group:

Melilite Group: Åkermanite, Alumoåkermanite, Gehlenite, Gugiaite, Hardystonite, Okayamalite

Varieties:

None

Synonyms:

None

Crystal Data

Crystallography:

Tetragonal - Scalenohedral

Crystal Habit:

In coarse, columnar masses; granular and as isolated grains.

Twinning:

None

Physical Properties

Cleavage:

Good on {001}, Poor on {100} and {110} 

Fracture:

Irregular/Uneven

Tenacity:

Brittle

Moh's Hardness:

3.0 - 4.0

Density:

3.396 - 3.443 (g/cm³)

Luminescence:

Fluorescent; dull to dark purple under SW UV, blue to violet blue under LW UV

Radioactivity:

Not Radioactive

Optical Properties

Color:

White, pale pinkish, light brownish white, grayish white; colorless in thin section.

Transparency:

Translucent

Luster:

Vitreous, Resinous, Dull

Refractive Index:

1.657 - 1.672  Uniaxial ( - ) 

Birefringence:

0.011

Dispersion:

n/a

Pleochroism:

None

Occurances

Geological Setting:

In granular ore in a metamorphosed stratiform zinc deposit.

Common Associations:

Vesuvianite, Apatite, Franklinite, Willemite, Rhodonite, Calcite, Dolomite

Common Impurities:

Al, Fe, Mn, Pb, Mg, Na

Type Locality:

Franklin Mine, Franklin, Franklin Mining District, Sussex Co., New Jersey, USA

Year Discovered:

1899

View mineral photos:

Hardystonite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Hardystonite is a calcium zinc silicate mineral that is usually a dull, unattractive white color in natural daylight but will fluoresce purple under short-wave (SW) ultraviolet (UV) light and blue to violet blue under logn-wave (LW) ultraviolet (UV) light. For this reason Hardystonite is well known to collectors of fluorescent minerals from Franklin and Sterling Hill, New Jersey. Fluorescence occurs when the ultraviolet light (invisible to humans) imparts energy to some of the atoms in the mineral. This energy is converted by the atom into visible light that we can then see.

Hardystonite is often found in association with other fluorescent minerals such as Calcite, Clinoherderite, Esperite, Fluorite, Willemite and Wollastonite. When two or more of these minerals are found together in one specimen it can make for wonderfully colorful fluorescent specimens. The purple or violet-blue color of Hardystonite really stands out among these minerals.

Distribution: From the type locality at Franklin Mine, Sussex County, New Jersey, USA. At Vrchlice River valley, Policany, Kutna Hora, Central Bohemian Region, Czech Republic. At Gottesbelohnung smelter, Hettstedt, Mansfeld Basin, Saxony-Anhalt, German. At Tsumeb, Otjikoto Region, Namibia. At Swietochlowice, Katowice, Upper Silesia (Slaskie), Poland.
 

  
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