Simonellite, C19H24, was first described from the lignite deposit of Fognano, Montepulciano, Siena Province, Tuscany, Italy, in 1919. Its crystal structure was solved and refined in the 1960s on the basis of recrystallized individuals. Notwithstanding several studies on this species, no type material has ever been reported. Following a new finding of simonellite, its crystal structure was re-examined using a natural crystal. Simonellite is orthorhombic, with space group Pnaa and unit-cell parameters a = 9.2220(5), b = 9.1269(5), c = 35.8907(17) Å, V = 3020.9(3) Å3. Its crystal structure was refined to R1 = 0.0513 for 2721 unique reflections with Fo > 4σ(F) and 244 refined parameters. Since no type material for this species is currently known, the studied material is defined as a neotype specimen for simonellite. It is deposited in the mineralogical collection of the Museo di Storia Naturale of the University of Pisa under catalogue number 20079.
Mauro et al. (Tue,) studied this question.