Larixite tries to be able to use any CIF file, but CIF is a complicated description of crystallographic information, and some CIF files from external sources may not be usable by Larixite. If you run into trouble, let us know, at larixite Github page or by emailing the developers.
The database of structures comes from data from American Mineralogist Crystal Structure Database that have been compiled into an SQLite3 database.
The code used here was originally part of xraylarch, but has now been migrated to its own project at larixite which can be used programmatically from Python.
The code to work with crystal structures and CIF files uses PyMatGen from the The Materials Project