Gerstleyite

Baker mine, U.S. Borax Mine (Pacific West Coast Borax Mine; Pacific Coast Borax Co. Mine; Boron Mine; U.S. Borax and Chemical Corp. Mine; Kramer Mine; Baker Mine), Kramer Borate deposit, Boron, Kramer District, Kern Co., California, USA
© Thomas Witzke

Show Gerstleyite Photos (4)

Formula:

(Sb,As)

·2H

System:

Monoclinic

Colour:

Cinnabar red, darkening ...

Lustre:

Sub-Adamantine

Hardness:

2½

Name:

Named after James Mack Gerstley (1907-2007), president of the Pacific Coast Borax Co.

As as red spherules with fibrous to platy structue up to 2.5 cm in clay with borates. This was the first known sodium sulfosalt.

Classification of Gerstleyite

IMA status:

Valid - first described prior to 1959 (pre-IMA) - "Grandfathered" 1956

Strunz 8th edition ID:

2/F.10-10

Nickel-Strunz 10th (pending) edition ID:

2.HE.05

2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
H : Sulfosalts of SnS archetype
E : With alkalies, H₂O

Dana 8th edition ID:

3.8.8.1

3 : SULFOSALTS
8 : 1 < ø < 2

Hey's CIM Ref.:

5.0.1

5 : Sulphosalts - Sulpharsenites and Sulphobismuthites (those containing Sn, Ge,or V are in Section 6)
0 : Sulpharsenites etc. of the alkali metals

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Type Occurrence of Gerstleyite

Type Locality:

Place of Conservation of Type Material:

Smithsonian, Harvard

Year of Discovery:

1956

Geological Setting of type material:

Low temperature Borate evaporite

Occurrences of Gerstleyite

Geological Setting:

As above

Physical Properties of Gerstleyite

Lustre:

Sub-Adamantine

Diaphaneity (Transparency):

Translucent

Colour:

Cinnabar red, darkening on exposure

Streak:

Bright cinnabar red

Hardness (Mohs):

2½

Hardness Data:

Measured

Tenacity:

Brittle

Cleavage:

Perfect
Perfect on 010 and 100,Poor on 001

Fracture:

None observed

Density (measured):

3.62 g/cm³

Density (calculated):

3.723 g/cm³

Crystallography of Gerstleyite

Crystal System:

Monoclinic

Class (H-M):

m - Domatic

Space Group:

Bm {B1 1m} {Cm} {C1m1}

Cell Parameters:

a = 9.911Å, b = 23.05Å, c = 7.097Å
α = 90°, β = 127.85°, γ = 90°

Ratio:

a:b:c = 0.43 : 1 : 0.308

Unit Cell Volume:

V 1,280.21 Å³ (Calculated from Unit Cell)

Morphology:

Fibrous and platy

X-Ray Powder Diffraction:

d-spacing		Intensity
11.85		(100)
3.05		(90)
5.64		(70)
4.03		(70)
2.81		(50)
2.739		(40)

Comments:

From type material at Baker Mine, Kern Co., Ca., USA

Optical Data of Gerstleyite

Type:

Biaxial

Dispersion:

r < v extreme

Pleochroism:

Weak

Comments:

X= salmon red, Y=Z= deep blood red

Chemical Properties of Gerstleyite

Formula:

(Sb,As)

·2H

Essential elements:

H, Na, O, S, Sb

All elements listed in formula:

As, H, Na, O, S, Sb

Analytical Data:

The analysis is not very good totalling 92%. The structure determination must have used better

             1         2        3
Na         4.28      4.65      3.29
Li         0.135     0.15
Sb        47.80     51.91     55.74
As         7.38      8.02      8.57
S         27.01     29.33     29.82
H^2O       5.47      5.94      2.58
gangue     n.d.
Total     92.07    100.00    100.00
1) Type material 2) same corrected to 100% 3)Na^2(Sb,As)^8S^13.2H^2O

Common Impurities:

Other Names for Gerstleyite

Other Languages:

German:	Gerstleyit
Russian:	Герслиит
Spanish:	Gerstleyita

Other Information

Health Warning:

No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.

Industrial Uses:

none

References for Gerstleyite

Reference List:

Frondel,C. and Morgan,V. (1956) Inderite and Gerstleyite From The Kramer borate district, Kern Co. California, American Mineralogist: 41: 839-843.

Nakai,I. and Appleman, D.E. (1981) The crystal structure of Gerstleyite Na^2(Sb.As)^8S^13.2H^2O: The first sulfosalt mineral of sodium. Chem. Lett: 1981(10): 1327-1330.

Geological Society of America, Program with Abstracts: 11(7): 485.

Chemical Abstracts: 95: 195617y.

Handbook vol 1, pg 181