Get a diffraction pattern and you can find out what it is!

First purify your sample by washing with ethanol or other organic solvents by ultra centrifugation, it will remove microbial residue and will also increase the concentration of prepared CdS particles. Then take your sample and try to lyophilize (freeze drying) it, Make sure your samples does not contain any moisture or other trace element. XRD is the best method to find and justify the crystalline nature of any sample. ( Sharp peaks represent good quality of sample and high crystallinity).

Thank you :)