Laphamite Mineral Data

General Laphamite Information

Chemical Formula:

As2(Se,S)3

Composition:

Molecular Weight = 351.55 gm

Arsenic 42.62 % As

Selenium 50.54 % Se

Sulfur 6.84 % S

______

100.00 %

Empirical Formula:

As₂Se_2.25S_0.75

Environment:

Secondary mineral formed as a sublimation product of a burning anthracite coal mine waste dump fire.

IMA Status:

Approved IMA 1986

Locality:

Burnside, Northumberland County, Pennsylvania, USA. Link to MinDat.org Location Data.

Name Origin:

Named for Davis M. Lapham (1931-1974), former Chief Mineralogist of the Pennsylvania Geological Survey.

Name Pronunciation:

Laphamite + Pronunciation

Synonym:

ICSD 29535

PDF 26-123

Laphamite Image

Images:

Laphamite

Comments: Brown grain of laphamite.
Location: Northumberland County, Pennsylvania, USA. Scale: Grain size 1.5 mm.
© Thomas Witzke / Abraxas-Verlag

Laphamite Crystallography

Axial Ratios:

a:b:c =1.2156:1:0.4371

Cell Dimensions:

a = 11.86, b = 9.756, c = 4.265, Z = 4; beta = 90.17° V = 493.48 Den(Calc)= 4.73

Crystal System:

Monoclinic - PrismaticH-M Symbol (2/m) Space Group: P 2₁/n

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

By Intensity(I/I_o): 2.833(1), 2.773(0.8), 4.87(0.7),

Crystal Structure:

Mouse
drag1 - LMB Manipulate Structure
drag2 - RMB Resize/Rotate
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S - Stereo Pair on/off
H - Help Screen
I - Data Info
A - Atoms On/Off
P - Polyhedra On/Off
B - Bonds On/Off
Help on Above

Bindi L , Bonazzi P , Spry P G , The Canadian Mineralogist , 46 (2008) p.269-274, Effects of sulfur-for-selenium substitution on the structure of laphamite, As2(Se,S)3, Locality: Western Middle Anthracite field, Northumberland County, Pennsylvania, Sample: LAP2

Physical Properties of Laphamite

Cleavage:

{010} Perfect

Color:

Dark red.

Density:

4.5

Diaphaneity:

Translucent to Subopaque

Fracture:

Flexible - Flexible fragments.

Habit:

Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).

Hardness:

1-2 - Between Talc and Gypsum

Luster:

Resinous

Streak:

red orange

Optical Properties of Laphamite

RL Anisotrophism:

Moderate, in tints of gray.

RL Color:

Gray-white, strong fiery red internal reflections, golden yellow near scratches.

RL Pleochroism:

Moderate, from white to gray.

Reflectivity

**Standardized Intensity (100%) Reflection Spectra of Laphamite in Air**
λ	R₁	R₂	∑ R₁(λ)	∑ R₂(λ)
400 nm	34.40	42.10
420 nm	33.90	41.00
440 nm	33.80	39.90
460 nm	33.80	38.80
480 nm	33.20	37.40
500 nm	32.30	36.30
520 nm	30.90	35.10
540 nm	29.50	34.00
560 nm	28.40	33.10
580 nm	27.60	32.30
600 nm	26.90	31.60
620 nm	26.40	31.10
640 nm	26.40	30.90
660 nm	26.30	30.60
680 nm	26.10	30.40
700 nm	25.90	30.10

**Calculated Relative Intensity Colors of Laphamite in Air**
Relative Intensity	0%	40%	80%	100%	120%	160%	200%	240%	280%	320%
R₁
R₂

Calculated Properties of Laphamite

Electron Density:

Bulk Density (Electron Density)=4.16 gm/cc
note: Specific Gravity of Laphamite =4.73 gm/cc.

Fermion Index:

Fermion Index = 0.03
Boson Index = 0.97

Photoelectric:

PE_Laphamite= 72.06 barns/electron
U=PE_Laphamite x rElectron Density= 299.59 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)
Laphamite is Not Radioactive

Laphamite Classification

Dana Class:

02.11.06.01 (02)Sulfides - Including Selenides and Tellurides

(02.11)where Am Bn Xp, with (m+n):p=2:3

(02.11.06)Dana Group

02.11.06.01 Laphamite As2(Se,S)3 P 2₁/n 2/m

Strunz Class:

02.FA.30 02 - SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulf

02.F - Sulfides of Arsenic, Alkalies; Sulfides with Halide, Oxide, Hydroxide, H2O

02.FA -With As, (Sb), S

02.FA.30 Orpiment As2S3 P 2₁/n 2/m

02.FA.30 Laphamite As2(Se,S)3 P 2₁/n 2/m

Other Laphamite Information

References:

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

See Also:

Links to other databases for Laphamite :
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 Laphamite here :
Ask-A-Mineralogist from the Mineralogical Society of America
Mindat.org's Discussion Groups
Original Rockhounds Discussion Group
Rockhounds Discussion Group on Yahoo Groups
Mineral Discussion Forum from Fabre Minerals - also available in Español

Print or Cut-and-Paste your Laphamite Specimen Label here :

Laphamite

As2(Se,S)3
Dana No: 02.11.06.01 Strunz No: 02.FA.30
Locality:

Notes: