Raygrantite is a mineral first discovered in Big Horn Mountains, Maricopa County, Arizona, US.[3] More specifically, it is located in the evening star mine, which is a Cu, V, Pb, Ag, Au, and W mine.[1] Raygrantite is a member of the iranite mineral group, which consists of hemihedrite, iranite, and raygrantite.[2] This mineral received its name in honor of Raymond W. Grant, a retired professor who primarily focused on the minerals of Arizona.[1] The typical crystal structure of raygrantite is bladed with parallel striations to the C axis. Its ideal chemical formula is Pb10Zn(SO4)6(SiO4)2(OH)2.[1] The IMA (International Mineralogical Association) approved raygrantite in 2013, and the first publication regarding this mineral was put forth in 2017.[3]
| Raygrantite | |
|---|---|
| General | |
| Category | Mineral |
| Formula (repeating unit) | Pb10Zn(SO4)6(SiO4)2(OH)2 |
| Crystal system | Triclinic |
| Crystal class | 1 – Pinacoidal |
| Space group | P1 |
| Unit cell | a = 9.3175(4) Å, b = 11.1973(5) Å c = 10.08318(5) Å; |
| Identification | |
| Formula mass | 2888 |
| Color | No color |
| Crystal habit | Bladed crystals |
| Twinning | Fishtail twining axis along [121] – twin axis along [010] |
| Cleavage | Good along {120} |
| Fracture | Uneven |
| Tenacity | Brittle |
| Mohs scale hardness | 3 |
| Luster | Vitreous |
| Streak | White |
| Diaphaneity | Transparent |
| Density | 6.374 g/cm3 |
| Optical properties | Biaxial positive |
| Refractive index | nα = 1.915(7) nβ = 1.981(7) nγ = 2.068(9) |
| Birefringence | δ = 0.153 |
| Dispersion | v < r strong |
| Absorption spectra | Z>Y>X |
| Solubility | Insoluble in water, acetone, and hydrochloric acid |
| References | [1][2][3] |
Occurrence
editRaygrantite is associated with cerussite, galena, mattheddleite, lanarkite, leadhillite, anglesite, alamosite, hydrocerussite, diaboleite, and caledonite.[3] Crystals were found in pockets encased in masses of galena.[1] Raygrantite is a secondary mineral and is the result of pyrite-galena-chalcopyrite veins. In this district of the Rocky Mountains, intrusions can date back to the late Cretaceous period.[1]
Physical properties
editRaygrantite is a colorless, transparent mineral that occurs in bladed crystal structures.[2] This bladed structure has striations parallel to the C-axis.[1] Its luster is vitreous, which means it looks similar to glass. Raygrantite on the Mohs hardness scale is a three, which is .5 softer than a penny. It exhibits brittle tenacity and has good cleavage along the {120} plain.[2] This mineral also has characteristic fishtail twinning along the {121} in addition to a twin axis along the {010}. This mineral's recorded density is 6.374 g/cm3.[1]
Optical properties
editRaygrantite is transparent with a vitreous luster. It is biaxial positive, which means it will refract light along two axes.[2] The mineral's 2Vmeas. 76° (2) and 2Vcalc. 85°. The refractive indices are: nα= 1.915(7) nβ= 1.981(7) nγ= 2.068(9).[3] Dispersion is strong, v < r. Raygrantite also exhibits absorption spectra of Z>Y>X.[1]
Chemical structure
editRaygrantite is isotypic with iranite and hemihedrite.[2] When looking at the chemical structure of the iranite mineral group, there are 10 symmetrically independent non-H cation sites. Of these sites, five are filled by lead Pb2þ (Pb1, Pb2, Pb3, Pb4, and Pb5).[1] Then three are filled by S6þ (S1, S2, and S3).[1] Finally, one of the sites is filled by Si4þ, and the last is filled by Zn2þ. Raygrantite is composed of layers of tetrahedron and octahedron joined together by lead ions.[2]
Chemical composition
edit| Oxide | wt% |
|---|---|
| SiO2 | 4.30 |
| SO3 | 16.49 |
| PbO | 74.91 |
| ZnO | 2.59 |
| H2O | [0.62] |
| Total | 98.81 |
X-ray crystallography
editTo collect this data, a Bruker X8 APEX2 CCD X-ray diffractometer equipped with graphite-monochromatized MoKa radiation was used.[1] Through these analyses, we can understand that Raygrantite is a member of the triclinic crystal system. It was also noted that the space group of this mineral is 1 – Pinacoidal.[2] The next conclusion that can be drawn from the X-ray diffraction data is the unit cell dimensions. These are as such: a = 9.3175(4) Å, b = 11.1973(5) Å
c = 10.08318(5) Å.[1]
See also
editReferences
edit- ^ a b c d e f g h i j k l m Yang H., Andrade B. M., Downs T. R., Gibbs B. R., Jenkins A. R. Raygrantite, Pb10Zn(SO4)6(SiO4)2(OH)2, A New Mineral Isostructural With Iranite, From The Big Horn Mountains, Maricopa County, Arizona, USA, The Canadian Mineralogist, 2016, rruff.info/rruff_1.0/uploads/CM54_625.pdf.
- ^ a b c d e f g h Slaughter, Dana. “Raygrantite: Mineral Information, Data and Localities.” Mindat.Org, 2017, zh.mindat.org/min-43868.html.
- ^ a b c d e f Raygrantite PB10ZN(So4 6(Sio4 2(OH)2 – Handbook of Mineralogy, Mineralogical Society of America, 2017, handbookofmineralogy.org/pdfs/raygrantite.pdf.