Crookesite Mineral Data

General Crookesite Information

Chemical Formula:

Cu7(Tl,Ag)Se4

Composition:

Molecular Weight = 940.92 gm

Thallium 16.29 % Tl

Copper 47.28 % Cu

Silver 2.87 % Ag

Selenium 33.57 % Se

______

100.00 %

Empirical Formula:

Cu₇Tl_0.75Ag_0.25Se₄

Environment:

Of hydrothermal origin, with other selenides.

IMA Status:

Valid Species (Pre-IMA) 1866

Locality:

From Skrikerum, near Tryserum, Kalmar, Sweden. Link to MinDat.org Location Data.

Name Origin:

After Sir William Crookes (1832-1919), who discovered thallium.

Synonym:

ICSD 69104

PDF 41-1457

Crookesite Image

Images:

Crookesite Eucairite

Comments: Polished section (PPL) showing zoned crystal of cream-colored eucairite and pale lavender crookesite along with steel blue umangite and white clausthalite in dark gray gangue..
Location: Mine dump (tailings) of Shaft 371 near Hartenstein/Saxony, Germany. Scale: Picture size 5 mm.
© Thomas Schlothauer

Crookesite Crystallography

Axial Ratios:

a:c = 1:0.37891

Cell Dimensions:

a = 10.435, c = 3.954, Z = 2; V = 430.55 Den(Calc)= 7.26

Crystal System:

Tetragonal - DisphenoidalH-M Symbol (4) Space Group: I 4

$Help on X Ray Diffraction:$ X Ray Diffraction:

By Intensity(I/I_o): 2.59(1), 3.29(1), 3(0.8),

Crystal Structure:

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Eriksson L , Werner P E , Berger R , Meerschaut A , Journal of Solid State Chemistry , 90 (1991) p.61-68, Structure refinement of TlCu7Se4 from X-ray powder profile data, Locality: synthetic, Sample: GH, Note: Cell parameters are an average of Table 1 values

View Additional jPOWD Structure files for Crookesite
[1] [2]

Physical Properties of Crookesite

Cleavage:

{???} Good

Color:

Blue gray, Brown pink, Gray.

Density:

6.9

Diaphaneity:

Opaque

Fracture:

Brittle - Generally displayed by glasses and most non-metallic minerals.

Habit:

Disseminated - Occurs in small, distinct particles dispersed in matrix.

Hardness:

2.5-3 - Finger Nail-Calcite

Luster:

Metallic

Optical Properties of Crookesite

RL Anisotrophism:

Weak but distinct, in brownish tones.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Crookesite in Air**
λ	R₁	R₂		∑ R₁(λ)	∑ R₂(λ)
400 nm	33.00	37.30

420 nm

32.60

37.40

440 nm

32.20

37.50

460 nm

31.80

37.40

480 nm

31.40

37.30

500 nm

31.40

37.00

520 nm

31.50

36.70

540 nm

31.50

36.50

560 nm

31.60

36.50

580 nm

31.70

36.60

600 nm

31.90

36.80

620 nm

32.20

37.00

640 nm

32.30

37.40

660 nm

32.50

37.80

680 nm

32.70

38.20

700 nm

32.80

38.60

**Calculated Relative Intensity Colors of Crookesite in Air**
Relative Intensity	0%	30%	60%	90%	100%	120%	150%	180%	210%	240%	270%	280%
R₁
R₂

Calculated Properties of Crookesite

Electron Density: Bulk Density (Electron Density)=6.35 gm/cc
note: Specific Gravity of Crookesite =7.26 gm/cc.

Fermion Index: Fermion Index = 0.02
Boson Index = 0.98

Photoelectric: PE_Crookesite= 331.04 barns/electron
U=PE_Crookesite x rElectron Density=2,102.14 barns/cc.

Radioactivity: GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Crookesite is Not Radioactive

Crookesite Classification

Dana Class: 02.04.12.01 (02)Sulfides - Including Selenides and Tellurides (02.04)where Am Bn Xp, with (m+n):p=2:1 (02.04.12)Dana Group

02.04.12.01 Crookesite Cu7(Tl,Ag)Se4 I 4 4

02.04.12.02 Sabatierite Cu4TlSe3 P 4/mmm 4/m 2/m 2/m

Strunz Class: 02.BD.50 02 - SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulf 02.B - Metal Sulfides, M:S > 1:1 (mainly 2:1) 02.BD -With Hg, Tl

02.BD.50 Crookesite Cu7(Tl,Ag)Se4 I 4 4

Other Crookesite Information

References: NAME( AntBidBlaNic1) PHYS. PROP.(Enc. of Minerals,2nd ed.,1990) OPTIC PROP.(AntBidBlaNic1)

See Also: Links to other databases for Crookesite :
1 - Am. Min. Crystal Structure Database
2 - Athena
3 - EUROmin Project
4 - Ecole des Mines de Paris
5 - GeoScienceWorld
6 - Google Images
7 - Google Scholar
8 - Handbook of Mineralogy (MinSocAm)
9 - Handbook of Mineralogy (UofA)
10 - MinDAT
11 - Mineralienatlas (Deutsch)
12 - Online Mineral Museum
13 - QUT Mineral Atlas
14 - Ruff.Info

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Ask about Crookesite here :
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Print or Cut-and-Paste your Crookesite Specimen Label here :

Crookesite

Cu7(Tl,Ag)Se4
Dana No: 02.04.12.01 Strunz No: 02.BD.50
Locality:

Notes: