Charlesite
Current inventory:  1 gem
 

  
Charlesite was named in honor of Dr. Charles Palache (1869–1954), eminent American crystallographer and mineralogist, Harvard University, Cambridge, Massachusetts, USA.

Discovered in 1945 (recognized in 1983);   IMA status: Valid (Approved 1983)

Chemistry

Chemical Formula:

Ca₆(Al,Si)₂(SO₄)₂B(OH)₄(OH,O)₁₂ · 26(H₂O)

Hydrated Calcium Aluminum Silicate Hydroborate Sulfate Hydroxide

Molecular Weight:

1,234.40 gm

Composition:

Calcium

19.48 %

Ca

27.26 %

CaO

Aluminum

3.28 %

Al

6.19 %

Al₂O₃

Silicon

1.14 %

Si

2.43 %

SiO₂

Boron

0.88 %

B

2.82 %

B₂O₃

Hydrogen

5.23 %

H

46.70 %

H₂O

Sulfur

5.20 %

S

12.97 %

SO₃

Oxygen

64.81 %

O

100.00 %

98.38 %

= TOTAL OXIDE

Classification

Mineral Classification:

Sulfates

Strunz 8th Ed. ID:

6/D.13-40

Nickel-Strunz 10th Ed. ID:

7.DG.15

7 : SULFATES (selenates, tellurates, chromates, molybdates, wolframates)
D : Sulfates (selenates, etc.) with additional anions, with H₂O
G : With large and medium-sized cations; with NO₃, CO₃, B(OH)₄, SiO₄ or IO₃

Related to:

Ettringite Group. Aluminum analogue of Sturmanite.

Members of Group:

Ettringite Group: Bentorite, Buryatite, Carraraite, Charlesite, Ettringite, Jouravskite, Micheelsenite, Sturmanite, Thaumasite

Varieties:

None

Synonyms:

IMA1981-043

Crystal Data

Crystallography:

Trigonal - Ditrigonal Pyramidal

Crystal Habit:

Crystals are tabular {0001}, dominated by {1014}, to 6 mm, may be rounded.

Twinning:

None

Physical Properties

Cleavage:

Perfect on {1010}

Fracture:

Conchoidal

Tenacity:

Brittle

Moh's Hardness:

2.5

Density:

1.77 (g/cm³)

Luminescence:

Pale violet to pale green fluorescence under SW UV, weaker pale green fluorescence under LW UV

Radioactivity:

Not Radioactive

Optical Properties

Color:

Colorless, White, pale Yellow, pale Pink

Transparency:

Transparent, may appear opaque due to surficial alteration.

Luster:

Vitreous to Dull

Refractive Index:

1.475 - 1.492  Uniaxial ( - )

Birefringence:

0.0170

Dispersion:

n/a

Pleochroism:

None observed

Occurances

Geological Setting:

Very rare, coating fractures and vugs in a metamorphosed stratiform zinc deposit.

Common Associations:

Clinohedrite, Ganophyllite, Xonotlite, Pectolite, Prehnite, “Mn-Chlorite”, Roeblingite, Willemite, Datolite

Common Impurities:

None

Type Locality:

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

Year Discovered:

1945 (recognized in 1983)

View mineral photos:

Charlesite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Charlesite is an extremely rare gem and a member of the Ettingite Group of minerals that includes Charlesite, Ettringite, Sturmanite and Thaumasite. It is also a very interesting mineral in that it is about 47% H₂O; almost half water! Faceted gems from the Wessels Mine in South Africa are an attractive, pale yellow, clean and usually small.

Charlesite was discovered in late 1945 by miners in the Franklin Mine in Franklin, Sussex County, New Jersey, and was brought to the attention of John L. Baum. This initial discovery was reported by Cornelius Hurlbut and John L. Baum in their report in 1960. They considered the new mineral to be a variety of Ettringite. It wasn't until an investigation of the mineral Sturmanite in 1983 that the new mineral was recharacterized as the aluminum analogue of Sturmanite and declared to be a separate, new mineral and named it Charlesite after Dr. Charles Palache (1869–1954), eminent American crystallographer and mineralogist, for his studies of the minerals of Franklin, New Jersery.

The only current sources of Charlesite are the Franklin Mine, Franklin, Sussex County, New Jersey, USA and the Wessel's Mine and N'Chwaning Mines, Kalahari manganese fields, Northern Cape Province, South Africa. The Wessel's Mine may be the only source of gem quality crystals.
 

  
Charlesite gems for sale: