Hi Khaoula, There are 16 form of ZnS ( based on the strongest lines) even though there are two types of crystalline (sphalerite and wurtzite). For example JCPDF-39-1363 ; 36-1460 (wurtzite), and JCPDF-05-0566 ; 03-0579 (sphalerite) and etc...You can search PCPDFWIN. Hope this will be useful.