Wulfenite
- Named in honour of Franz Xavier Wulfen (1728–1805), Austrian–German Jesuit, who wrote a monograph on the lead ores of Bleiberg, Austria.
- Wulfenite was voted “Mineral of the Year” in Austria in 2020.
- In its pure form wulfenite is colorless; the often yellow to red colour is most probably due to trace amounts of chromium substituting Mo.
- Formula: PbMoO4
- Space group: I41/a (No. 88)
- Crystal system: tetragonal
- Crystal class: 4/m
- Lattice parameters: a = b = 5.434 Å, c = 12.107 Å, α = β = γ = 90°
Modified by CombineZP
Picture: Didier Descouens – CC BY-SA 4.0
https://commons.wikimedia.org/w/index.php?curid=12426342
Crystal structure (click on the picture to download the VESTA file):
(K. Momma and F. Izumi, “VESTA 3 for three-dimensional visualization of crystal, volumetric and morphology data,”J. Appl. Crystallogr., 44, 1272-1276 (2011).)
- PbO8 coordination environment
- MoO4 tetrahedra (blue)
- Pb (black)
- Oxygen (red)
For a 3D interactive version on sketchfab, see here:
Reference:
Natural wulfenite: structural refinement by single-crystal X-ray diffraction
C. Lugli, L. Medici, D. Saccardo,
Neues Jahrbuch fur Mineralogie, Monatshefte 1999, 6, 281-288
The Fascination of Crystals and Symmetry 
Yes, the color change is caused by the Cr substitution. Here is the paper with more details about color and also presence of OH groups in wulfenite: https://www.researchgate.net/profile/Dominik_Talla/publication/257391396_On_the_presence_of_hydrous_defects_in_differently_coloured_wulfenites_PbMoO4_An_infrared_and_optical_spectroscopic_study/links/54b12bc40cf28ebe92dff6aa/On-the-presence-of-hydrous-defects-in-differently-coloured-wulfenites-PbMoO4-An-infrared-and-optical-spectroscopic-study.pdf
Thank you very much for your contribution and for pointing to the paper!
best wishes
Frank