Laphamite Mineral Data

Laphamite Mineral Data +

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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.

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),

Physical Properties of Laphamite

Cleavage:

[010] Perfect

Color:

Dark red.

Density:

4.5

Diaphaniety:

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:

r_electron=4.16 gm/cc
note: r_Laphamite=4.73 gm/cc.

Fermion Index

Fermion Index = 0.03892
Boson Index = 0.96108

Photoelectric:

PE_Laphamite= 72.06 barns/electron
U=PE_Laphamite x r_electron= 299.59 barns/cc.

Radioactivity:

GRapi = 0 (Gamma Ray American Petroleum Institute Units)

Laphamite is Not Radioactive

Laphamite Classification

Dana Class:

2.11.6.1 (2)Sulfides - Including Selenides and Tellurides

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

(2.11.6)Dana Group

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

Strunz Class:

II/F.02-80 II - Sulfides and sulphosalts

II/F - Sulfides with nonmetallic properties, Arsenic-Sulfides

II/F.02 - Duranusite - Jeromite series

II/F.02-10 Duranusite As4S Unk Ortho

II/F.02-20 Dimorphite As4S3 P nma 2/m 2/m 2/m

II/F.02-30 Realgar AsS P 2₁/n 2/m

II/F.02-40 Pararealgar AsS P 2₁/c 2/m

II/F.02-50 Alacranite As8S9 P 2/c 2/m

II/F.02-60 Uzonite As4S5 P 2₁/m 2/m

II/F.02-70 Orpiment As2S3 P 2₁/n 2/m

II/F.02-80 Laphamite As2(Se,S)3 P 2₁/n 2/m

II/F.02-90 Jeromite As(S,Se)2 None

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 -Google Images 5 -Google Scholar 6 -Handbook of Mineralogy (UofA) 7 -MinDAT 8 -MinMax(Deutsch) 9 -MinMax(English) 10 -Mineralienatlas (Deutsch) 11 -QUT Mineral Atlas 12 -École des Mines de Paris

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Laphamite

As2(Se,S)3
Dana No: 2.11.6.1 Strunz No: II/F.02-80
Locality:

Notes: