Brillouin and Raman spectroscopy of the ferroelastic rutile-to-CaCl2 transition in SnO2 at high pressure: by Holger Hellwig, Alexander F. Goncharov, Eugene Gregoryanz, Ho-kwang Mao, and Russell J. Hemley
Phys. Rev. B 67, 174110 (2003)
I have found unusual pure cassiterite crystals with Raman spectroscopy, which show substantial differences from cubic, tetragonal, and orthorhombic cassiterite. See K. Balakrishnan et al. (2022).