Hodgkinsonite
Current inventory:  0 gems
 

  
Hodgkinsonite is named for H.H. Hodgkinson, Assistant Underground Superintendent of the Franklin mine, who discovered the mineral.

Discovered in 1913. IMA status: Valid (pre-IMA; Grandfathered)

Chemistry

Chemical Formula:

Mn²⁺Zn₂(SiO₄)(OH)₂

Zinc Manganese Silicate Hydroxide

Molecular Weight:

311.82 gm

 Composition:

Manganese

17.62 %

Mn

22.75 %

MnO

Zinc

41.94 %

Zn

52.20 %

ZnO

Silicon

9.01 %

Si

19.27 %

SiO₂

Hydrogen

0.65 %

H

5.78 %

H₂O

Oxygen

30.79 %

O

100.00 %

100.00 %

= TOTAL OXIDE

Classification

Mineral Classification:

Silicates (Germanates)

Strunz 8th Ed. ID:

8/B.01-10

Nickel-Strunz 10th Ed. ID:

9.AE.20

9 : SILICATES (Germanates)
A : Nesosilicates
E : Nesosilicates with additional anions (O,OH,F,H₂O); cations in tetrahedral [4] coordination

Related to:

Euclase Group

Varieties:

n/a

Synonyms:

n/a

Crystal Data

Crystallography:

Monoclinic - Prismatic

Crystal Habit:

As euhedral crystals, stout prismatic and terminated by steep pyramids, also dominated by pyramidal forms, to 2 cm. Granular to massive in veinlets.

Twinning:

None

Physical Properties

Cleavage:

Perfect on {001}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

4.5 - 5.0

Density:

4.06 - 4.08 (g/cm³)

Luminescence:

Not often fluorescent, but some specimens have shown a red, weak pink or dull dark purple fluorescence under longwave UV light.

Radioactivity:

Not Radioactive

Optical Properties

Color:

Bright Pink or Red to Reddish Brown and Orange, rarely Yellow; Black from tarnish or inclusions.

Transparency:

Transparent, Translucent to Opaque

Luster:

Vitreous

Refractive Index:

1.720 - 1.746  Biaxial ( - )

Birefringence:

0.0260

Dispersion:

Strong to moderate; r > v or r < v

Pleochroism:

Distinct; in shades of lavender and pale purple.

Occurances

Geological Setting:

As seams in massive willemite-franklinite granular ore in a metamorphosed stratiform zinc deposit (Franklin, New Jersey, USA).

Common Associations:

Barite, Willemite, Franklinite, Tephroite, Pyrochroite, Calcite, Manganoan Garnet, Copper.

Common Impurities:

Fe, Mg, Ca

Co-Type Localities:

• Franklin Mine, Franklin, Franklin Mining District, Sussex County, New Jersey, USA
• Hamburg Mine (Hamburg Road Mine), Franklin, Franklin Mining District, Sussex County, New Jersey, USA

Year Discovered:

1913

View mineral photos:

Hodgkinsonite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Hodgkinsonite is an extremely rare mineral and gem. Hodgkinsonite is one of the rarest of all collector gems. It was discovered in 1913 at the Franklin Mining District, Sussex County, New Jeresey, USA. This is the only location for finding Hodgkinsonite in the world. It is one of several minerals found at this location and nowhere else. Hodgkinsonite was mined out years ago and the mines have been closed. Hodgkinsonite is the product of the metamorphism of other zinc minerals such as Hemimorphite and Smithsonite. It is a very attractive mineral that is found in bright pink to lavender colors. Gems can be very attractive with colors of bright pink, red to reddish brown, orange, or rarely yellow but are typically very small due to small crystal sizes.
 

  
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