Fiedlerite and others minerals with similar chemistries belong to a division in the Halide Class called the Oxyhalides and Hydroxyhalides . These minerals have either oxygen or hydroxide groups in their chemistries. The oxygen atom in their chemistries might require their classification in the Oxides Class of minerals except that their structures are more tied to the halide elements and the oxygens and hydroxides are kind of superfluous to the overall structure. Color is colorless and white. Luster is adamantine.
Crystals are transparent to translucent.
Crystal Habits include tiny tabular to platy crystals. Cleavage is good, but not discernible. Fracture is conchoidal. Hardness is 3.5 . Streak is white.