Laphamite
A valid IMA mineral species
This page kindly sponsored by Donald Lapham
About Laphamite
Davis M. Lapham
Formula:
As2Se3
Colour:
Dark red
Lustre:
Resinous
Hardness:
1 - 2
Specific Gravity:
4.5
Crystal System:
Monoclinic
Name:
Named in honor of Davis M. Lapham (5 May 1931, Glens Falls, New York, USA - 20 December 1974, Harrisburg, Pennsylvania, USA), former Chief Mineralogist of the Pennsylvania Geological Survey. In addition to his technical work, he wrote several collector-friendly publications including 'Mineral Collecting in Pennsylvania'. He was a founding member of the Friends of Mineralogy.
Type Locality:
Isostructural with:
The Se analogue of orpiment. Compare kalgoorlieite - the chemical (Te) analogue, but not isostructural with laphamite.
Caveat: Some (or all?) of the photographs showing yellow acicular material might depict Se-bearing orpiment rather than laphamite. (See discussion at https://www.mindat.org/forum.php?read,7,361533,391404#msg-391404 )
Caveat: Some (or all?) of the photographs showing yellow acicular material might depict Se-bearing orpiment rather than laphamite. (See discussion at https://www.mindat.org/forum.php?read,7,361533,391404#msg-391404 )
Unique Identifiers
Mindat ID:
2328
Long-form identifier:
mindat:1:1:2328:9
IMA Classification of Laphamite
Approved
Approval year:
1985
First published:
1986
Classification of Laphamite
2.FA.30
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
F : Sulfides of arsenic, alkalies; sulfides with halide, oxide, hydroxide, H2O
A : With As, (Sb), S
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
F : Sulfides of arsenic, alkalies; sulfides with halide, oxide, hydroxide, H2O
A : With As, (Sb), S
2.11.6.1
2 : SULFIDES
11 : AmBnXp, with (m+n):p = 2:3
2 : SULFIDES
11 : AmBnXp, with (m+n):p = 2:3
3.7.10
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
7 : Sulphides etc. of V, As, Sb and Bi
3 : Sulphides, Selenides, Tellurides, Arsenides and Bismuthides (except the arsenides, antimonides and bismuthides of Cu, Ag and Au, which are included in Section 1)
7 : Sulphides etc. of V, As, Sb and Bi
Mineral Symbols
As of 2021 there are now IMA–CNMNC approved mineral symbols (abbreviations) for each mineral species, useful for tables and diagrams.
| Symbol | Source | Reference for Standard |
|---|---|---|
| Lpm | IMA–CNMNC | Warr, L.N. (2021). IMA–CNMNC approved mineral symbols. Mineralogical Magazine, 85(3), 291-320. doi:10.1180/mgm.2021.43 |
Physical Properties of Laphamite
Resinous
Transparency:
Opaque
Colour:
Dark red
Streak:
Red-orange
Hardness:
1 - 2 on Mohs scale
Tenacity:
Malleable
Cleavage:
Perfect
On {010}
On {010}
Density:
4.5(1) g/cm3 (Measured) 4.60 g/cm3 (Calculated)
Optical Data of Laphamite
Anisotropism:
Moderate with grey rotation tints.
Bireflectance:
Moderate, white to grey.
Reflectivity:
| Wavelength | R1 (%) | R2 (%) | imR1 (%) | imR2 (%) |
|---|---|---|---|---|
| 400nm | 34.4% | 42.1% | 19.6% | 26.2% |
| 420nm | 33.9% | 41.0% | 18.8% | 25.1% |
| 440nm | 33.8% | 39.9% | 18.7% | 24.0% |
| 460nm | 33.8% | 38.8% | 18.5% | 22.8% |
| 480nm | 33.3% | 37.5% | 17.9% | 21.5% |
| 500nm | 32.3% | 36.3% | 17.0% | 20.4% |
| 520nm | 30.9% | 35.1% | 15.8% | 19.3% |
| 540nm | 29.5% | 34.0% | 14.6% | 18.3% |
| 560nm | 28.4% | 33.1% | 13.6% | 17.5% |
| 580nm | 27.6% | 32.3% | 13.0% | 16.8% |
| 600nm | 26.9% | 31.6% | 12.4% | 16.3% |
| 620nm | 26.4% | 31.1% | 12.1% | 15.9% |
| 640nm | 26.4% | 30.9% | 12.3% | 15.9% |
| 660nm | 26.3% | 30.6% | 12.5% | 15.9% |
| 680nm | 26.1% | 30.4% | 12.4% | 15.8% |
| 700nm | 25.9% | 30.1% | 12.3% | 15.8% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 42.1%.
R1 shown in black, R2 shown in red, imR1 shown in green, imR2 shown in blue
Internal Reflections:
Fiery red; also golden yellow along scratches.
Pleochroism:
Not Visible
Chemistry of Laphamite
Mindat Formula:
As2Se3
Elements listed:
Crystallography of Laphamite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Cell Parameters:
a = 11.86(1) Å, b = 9.756(9) Å, c = 4.265(9) Å
β = 90.17(30)°
β = 90.17(30)°
Ratio:
a:b:c = 1.216 : 1 : 0.437
Unit Cell V:
493.5 ų
Z:
4
Morphology:
Crystals are tabular on (010), elongate on [100], and are composed of the forms {100}, {1l0}, {101}, and {301}.
Comment:
P21/n
Crystal Structure
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Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
Unit Cell | Unit Cell Packed
2x2x2 | 3x3x3 | 4x4x4
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Data courtesy of the American Mineralogist Crystal Structure Database. Click on an AMCSD ID to view structure
| ID | Species | Reference | Link | Year | Locality | Pressure (GPa) | Temp (K) |
|---|---|---|---|---|---|---|---|
| 0006182 | Laphamite | Bindi L, Bonazzi P, Spry P G (2008) Effects of sulfur-for-selenium substitution on the structure of laphamite, As2(Se,S)3 The Canadian Mineralogist 46 269-274 |  | 2008 | Western Middle Anthracite field, Northumberland County, Pennsylvania | 0 | 293 |
| 0006181 | Laphamite | Bindi L, Bonazzi P, Spry P G (2008) Effects of sulfur-for-selenium substitution on the structure of laphamite, As2(Se,S)3 The Canadian Mineralogist 46 269-274 | | 2008 | Western Middle Anthracite field, Northumberland County, Pennsylvania | 0 | 293 |
| 0010945 | Laphamite | Stergiou A C, Rentzeperis P J (1985) The crystal structure of arsenic selenide, As2Se3 Zeitschrift fur Kristallographie 173 185-191 | | 1985 | synthetic | 0 | 293 |
CIF Raw Data - click here to close
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 2.833 Å | (100) |
| 2.773 Å | (80) |
| 4.87 Å | (70) |
| 2.905 Å | (60) |
| 1.777 Å | (50) |
| 1.709 Å | (50) |
| 3.72 Å | (40) |
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| Stage 10a: Neoproterozoic oxygenation/terrestrial biosphere | <0.6 |
| 50 : Coal and/or oil shale minerals | <0.36 |
| Stage 10b: Anthropogenic minerals | <10 Ka |
| 54 : Coal and other mine fire minerals (see also #51 and #56) |
Type Occurrence of Laphamite
General Appearance of Type Material:
Dark red euhedral crystals, to 5.0 mm.
Place of Conservation of Type Material:
The Natural History Museum, London, England, 1984,843 and E.1036.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 163039.
National Museum of Natural History (Smithsonian), Washington, D.C., USA, 163039.
Geological Setting of Type Material:
Secondary mineral formed, probably by sublimation, on a clinker adjacent to a surface vent on a burning pile of coal.
Associated Minerals at Type Locality:
Synonyms of Laphamite
Other Language Names for Laphamite
Common Associates
Associations Based on Photo Data:
| 6 photos of Laphamite associated with Arsenolite | As2O3 |
| 1 photo of Laphamite associated with Native Sulphur | S8 |
| 1 photo of Laphamite associated with 'Unnamed (NH4-Al Fluoride)' | (NH4)AlF4 |
Related Minerals - Strunz-mindat Grouping
| 2.FA. | Bonazziite | As4S4 |
| 2.FA. | Anorpiment | As2S3 |
| 2.FA. | Paradimorphite | As4S3 |
| 2.FA.05 | Duranusite | As4S |
| 2.FA.10 | Dimorphite | As4S3 |
| 2.FA.15b | Pararealgar | As4S4 |
| 2.FA.15a | Realgar | As4S4 |
| 2.FA.15d | 'UM1970-18-S:As' | As4S4 |
| 2.FA.20 | Alacránite | As8S9 |
| 2.FA.25 | Uzonite | As4S5 |
| 2.FA.30 | Orpiment | As2S3 |
| 2.FA.35 | Getchellite | AsSbS3 |
| 2.FA.40 | Wakabayashilite | [(As,Sb)6S9][As4S5] |
| 2.FA.40 | Kalgoorlieite | As2Te3 |
Other Information
Health Risks:
No information on health risks for this material has been entered into the database. You should always treat mineral specimens with care.
Internet Links for Laphamite
mindat.org URL:
https://www.mindat.org/min-2328.html
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References for Laphamite
Reference List:
Stergiou, A. C., Rentzeperis, P. J. (1985) The crystal structure of arsenic selenide, As2Se3. Zeitschrift für Kristallographie - Crystalline Materials, 173 (3) 185-191 doi:10.1524/zkri.1985.173.3-4.185
Dunn, Pete J., Peacor, Donald R., Criddle, Alan J., Finkelman, Robert B. (1986) Laphamite, an arsenic selenide analogue of orpiment, from burning anthracite deposits in Pennsylvania. Mineralogical Magazine, 50 (356) 279-282 doi:10.1180/minmag.1986.050.356.11
Hawthorne, Frank C., Jambor, John L., Bladh, Kenneth W., Burke, Ernst A. J., Grice, Joel D., Phillips, Don, Roberts, Andrew C., Schedler, Robert A., E., James (1987) New mineral names. American Mineralogist, 72 (9-10) 1023-1028
Localities for Laphamite
Showing 1 localities.
symbol to view information about a locality.
The Locality List
- This locality has map coordinates listed.
- This locality has estimated coordinates.
ⓘ - Click for references and further information on this occurrence.
? - Indicates mineral may be doubtful at this locality.
- Good crystals or important locality for species.
- World class for species or very significant.
(TL) - Type Locality for a valid mineral species.
(FRL) - First Recorded Locality for everything else (eg varieties).
All localities listed without proper references should be considered as questionable.
USA (TL) | |
| Dunn et al. (1986) |
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Burnside, Northumberland County, Pennsylvania, USA