I assume you guys get thousands of these. Well here goes. 'Several' stories in 1 book, read in the early 80's, dating at least as far back as the 70's and 60's maybe.
Story one is some kind of planetary exploration team. One group comes back into camp bleeding to death and missing fingers. On the wind is some kind of whistling noise, than all these armadillo sized diamond/glass creatures come over the horizon and attack, very fast and sharp little buggers, crew fights back melting some of them with some kind of laser guns, not sure how it ends.
Story two is some other planet, a 'rite of passage' I think where some kid drinks the blood of some creature that has its neck punctured at a ceremony. Basically it turns him into a vampire...
And a couple other stories in the book, mainly after the first story.