This sample is impure and is a mixture of bauxite minerals including gibbsite, kaolinite and a very small amount of a ferruginous material. Oxides and hydroxides. Modern Geology, v. 2, p. 195-205.
Small grains coat larger grains.
Large grains are translucent and this makes it difficult to obtain optical properties. I recomment that this sample be x-rayed for proper identification. No fizz with HCl.