These two stories are early Balzac. Sarrasine is a spook story without a spook and A Passion in the Desert is set in Egypt. Not typical. But, then, I'm not sure there is such a thing as typical Balzac. I'm tempted to say he started off Delacroix and ended up Manet, but that would be an oversimplification. The two modes, romanticism and realism, are always present in his work. The story of Lucien de Rubempre (Illusions Perdues and Splendeurs et Miseres) starts off as social realism but then Vautrin enters the frame and everyone is plotting and putting on disguises and throwing one another off roofs and we're into the world of Fantomas.
Sarrasine is very famous (at least in France) because Roland Barthes rolled all over it, like a dog with a dead rabbit, and produced S/Z- a foundation text of post-structuralism (it may be wonderful; I haven't read it). Sarrasine could almost be Poe- only Poe writes better prose, is largely innocent of the way of the world and the girl in it isn't dead but...well- that would be giving the game away.
A Passion in the Desert is a love story- boy meets leopard- and bracingly unsentimental.