CorelMOSAIC is an image management and gallery application. It is a component of CorelDRAW.
A CorelMOSAIC library is an image collection, in the form of a pair of files: .CLB and .CLH. The CLB file contains thumbnail images and some metadata. The CLH file contains the full image files.
The CLB file can probably be identified fairly reliably from its contents, but not in a nice easy way. It has no signature, and starts with a variable-length filename field.
The CLH file is just an LHA compressed archive, with an unconventional filename extension.
See also LHA#Software.