The structural, optical and related properties (i.e. photoluminescence, photoconductivity etc.) of some natural three- and lower-dimensional semiconductor systems based on metal halides are briefly reviewed and some new results are reported. A blue shift of the excitonic bands was observed by decreasing the dimensionality or the size of the materials active part. The results are similar to those obtained from conventional semiconductor systems (e.g. GaAs, CdS, PbI2) by decreasing artificially the dimensionality or decreasing the size.