Danielsite

Danielsite is a sulfide and sulfosalt that was first discovered in a pocket of supergene minerals in the north region of Western Australia. The location found was about 1 kilometre (0.62 mi) west of the locality known as Coppin Pool. The mineral danielsite was named after John L. Daniels who collected the sample in which the new mineral was found. The chemical formula of danielsite is (Cu,Ag)
14
HgS
8
. Danielsite is very fine grained and hard to observe in hand samples. It generally has a gray color with very brittle and soft physical characteristics. [4]

Danielsite
General
CategorySulfide and Sulfosalt
Formula
(repeating unit)
(Cu,Ag)
14
HgS
8
Strunz classification2/B.09-10
Dana classification2.16.7.2
Crystal systemOrthorhombic
Space groupn.d.
Unit cella = 9.644[Å]
b = 9.180[Å]
c = 18.156[Å]
Z = 4
Identification
ColorGray
Crystal habitMicroscopic Crystals 20 micron masses in anglesite
TenacityBrittle
Mohs scale hardness1.5-2.5
LusterMetallic
Diaphaneityopaque
Specific gravity6.541 g/cm3 (calculated)
Density6.541 g/cm3 (calculated)
Optical propertiesAnisotropic
BirefringenceWeak
References[1][2][3]

Occurrence

Danielsite occurs in the mineral anglesite as ragged polycrystalline masses typically intergrown with covellite, stromeyerite, and chalcocite. The size of these masses is typically 20 micrometres (0.00079 in) across. Due to its occurrence with stromeyerite it is thought to possibly be a polymorphic replacement of galena. Danielsite was found in a gossanous pod in a white quartz vein. It has been found near Coppin Pool, Ashburton Shire, Western Australia, Australia, Austria, and Belgium.[4]

Physical properties

Danielsite is a metallic-gray mineral that looks a lot like stromeyerite, the main difference between the two is that stormeyerites colors are yellow to brown whereas danielsite is gray. Danielsite is very soft and brittle with only a 1.5-2.5 on the mohs hardness scale (VHN10 hardness of 38). There is no discernible type of cleavage, but due to the small size of the crystallites the possibility of cleavage can't be 100% excluded. It is a rather dense mineral weighing in at 6.541 g/cm3.[4]

Chemical composition

Element wt% Range
Cu 33.9 32.5-34.6
Ag 36.5 35.8-37.1
Hg 12.3 12.2-12.4
S 16.1 15.8-16.3

The data for this chart was gathered using a polished section by electron microprobe and using a crystal spectrometer with the following standards: galena (S), cinnabar (Hg), and metals (Ag and Cu). The results were calculated on the basis of 23 atoms due to its chemical formula being very similar to balkanite. [4]

X-Ray crystallography

The sample found was ground up and an X-ray powder diffraction was done to the powder. The pattern had a few places that appeared to be anglesite but overall the pattern didn't match up with any other mineral known. Most of the values could be measured on a triclinic unit cell but the d values of the actual data and calculated data varied by a lot. Most sulfides do not belong to the triclinic system as well, so it was thought that this was the wrong choice for danielsite.[4] More research was done on this mineral by Nickel and Kato and they both came to the conclusion that danielsite has an orthorhombic unit cell. When they tried calculating the d values based on the orthorhombic system the values came back very similar. Even though danielsite and balkanite have very similar chemical formulas their unit cells are vastly different. From the reported occurrences of the two minerals it is apparent that balkanite is the high temperature form and danielsite is the low-temperature form.[5]

I est D obs D calc[5] hkl
2 4.44 4.450 021
1 4.11 4.107 104
4.096 022
2 3.648 3.657 023
3.631 005
0.5 3.493 3.488 213
0.5 3.401 3.398 105
1 3.314 3.325 220
3.305 204
.5 3.198 3.187 115
2B 3.018 3.026 006
3.017 031
.5 2.885 2.887 106
2.880 131
3 2.831 2.839 303
10 2.622 2.627 133
2.623 304
1 2.564 2.563 206
2.558 231
1 2.475 2.469 216
5 2.392 2.407 305
2.390 401
0.5 2.222 2.225 042
2.217 217
1 2.080 2.081 333
2.078 422
1 2.034 2.034 028
1 1.991 1.992 334
1.991 128
1.986 326
6 1.959 1.960 243
6 1.875 1.877 511
1.874 228
2 1.692 1.692 147
1 1.642 1.638 055
.5 1.588 1.590 239
1.589 346
1.588 351
0.5 1.512 1.513 0.0.12
1.512 621
1.511 455
.5 1.425 1.427 058
1.426 2.1.12
1.424 0.4.10
1B 1.279 1.280 1.5.10
1.279 462
1 1.259 1.258 168
1.257 609

See also

  • List of Minerals
  • Classification of minerals

References

  1. Danielsite in Handbook of Mineralogy (PDF) . Retrieved on 2017-11-06.
  2. Danielsite at Mindat.org
  3. Danielsite at webmineral.com
  4. Nickel, E. H. (1987). "Danielsite: A new sulfide mineral from Western Australia". The American Mineralogist. 72 (3–4): 401–403.
  5. Kato, A.; Nickel, E. H. (1988). "Possible unit cell for danielsite". The American Mineralogist. 73: 187–188.
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