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Ferdowsiite
A valid IMA mineral species
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About Ferdowsiite
Ferdowsi Tousi
Formula:
Ag8(Sb5As3)S16
A Pb-bearing variety was also described (Makovicky et al., 2013).
Colour:
Greyish black
Lustre:
Metallic
Hardness:
2½ - 3
Specific Gravity:
5.3 (Calculated)
Crystal System:
Monoclinic
Name:
The name is for one of the greatest Persian personalities, Ferdowsi Tousi (935–1020), one of the greatest Persian poets to have ever lived. His life-long endeavor to preserve the national identity, language and heritage of his homeland, especially through one of the greatest poetic masterpieces, the Shahnameh, won him lasting fame and honor.
Superstructure of PbS.
Member of the group of ABX2-type sulfosalts of silver, combining antimony and arsenic, with a crystal structure different from other members of this group.
Related to sangenaroite and ~Sb5As3 analogue of the latter.
Member of the group of ABX2-type sulfosalts of silver, combining antimony and arsenic, with a crystal structure different from other members of this group.
Related to sangenaroite and ~Sb5As3 analogue of the latter.
Unique Identifiers
Mindat ID:
43594
Long-form identifier:
mindat:1:1:43594:7
IMA Classification of Ferdowsiite
Approved
IMA Formula:
Ag1+8(Sb3+5As3+3)S2-16
Approval year:
2012
First published:
2013
Classification of Ferdowsiite
2.JA.
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
J : Sulfosalts of PbS archetype
A : Galena derivatives with little or no Pb
2 : SULFIDES and SULFOSALTS (sulfides, selenides, tellurides; arsenides, antimonides, bismuthides; sulfarsenites, sulfantimonites, sulfbismuthites, etc.)
J : Sulfosalts of PbS archetype
A : Galena derivatives with little or no Pb
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 |
|---|---|---|
| Fdw | 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 Ferdowsiite
Metallic
Transparency:
Opaque
Colour:
Greyish black
Streak:
Dark grey
Hardness:
2½ - 3 on Mohs scale
Comment:
estimated
Tenacity:
Brittle
Cleavage:
None Observed
Parting:
None observed
Fracture:
Irregular/Uneven
Density:
5.3 g/cm3 (Calculated)
Comment:
Could not be measured due to lack of material.
Optical Data of Ferdowsiite
Anisotropism:
Distinct in air, and further enhanced in oil. Rotation tints vary between dark brown and bluish grey
Bireflectance:
Distinct
Reflectivity:
| Wavelength | R1 (%) | R2 (%) |
|---|---|---|
| 400nm | 32.3% | 37.4% |
| 420nm | 36.1% | 38.5% |
| 440nm | 35.7% | 37.8% |
| 460nm | 35.1% | 37.3% |
| 470nm | 34.9% | 37.3% |
| 480nm | 34.9% | 37.4% |
| 500nm | 34.3% | 37.1% |
| 520nm | 34.1% | 36.7% |
| 540nm | 33.5% | 36.3% |
| 546nm | 33.4% | 35.9% |
| 560nm | 33.3% | 35.9% |
| 580nm | 32.4% | 35.3% |
| 589nm | 32.4% | 35.1% |
| 600nm | 32.3% | 35.1% |
| 620nm | 31.8% | 34.4% |
| 640nm | 31.0% | 33.8% |
| 650nm | 30.7% | 33.5% |
| 660nm | 30.4% | 33.0% |
| 680nm | 29.8% | 32.6% |
| 700nm | 29.2% | 31.9% |
Graph shows reflectance levels at different wavelengths (in nm). Peak reflectance is 38.5%.
R1 shown in black, R2 shown in red
Colour in reflected light:
Greyish white
Internal Reflections:
Not observable
Pleochroism:
Visible
Comments:
Distinct, white to grey
Chemistry of Ferdowsiite
Mindat Formula:
Ag8(Sb5As3)S16
A Pb-bearing variety was also described (Makovicky et al., 2013).
A Pb-bearing variety was also described (Makovicky et al., 2013).
Element Weights:
Elements listed:
Crystallography of Ferdowsiite
Crystal System:
Monoclinic
Class (H-M):
2/m - Prismatic
Space Group:
P21/c
Setting:
P21/n
Cell Parameters:
a = 8.677(2) Å, b = 5.799(1) Å, c = 13.839(3) Å
β = 96.175(4)°
β = 96.175(4)°
Ratio:
a:b:c = 1.496 : 1 : 2.386
Unit Cell V:
692.28 ų
Z:
1
Morphology:
Elongated crystals
X-Ray Powder Diffraction
Powder Diffraction Data:
| d-spacing | Intensity |
|---|---|
| 3.225 Å | (96) |
| 3.205 Å | (100) |
| 2.900 Å | (78) |
| 2.750 Å | (90) |
| 2.707 Å | (73) |
| 1.998 Å | (41) |
| 1.979 Å | (39) |
| 1.940 Å | (22) |
Reference:
Comments:
From Type Description.
Geological Environment
Paragenetic Mode(s):
| Paragenetic Mode | Earliest Age (Ga) |
|---|---|
| High-𝑇 alteration and/or metamorphism | |
| 33 : Minerals deposited by hydrothermal metal-rich fluids (see also [#12]) |
Uchucchacua Mine, Uchucchacua area, Oyón District, Oyón Province, Lima, Peru