I would be sure to test the one in the middle bottom with vinegar (in the final picture) that looks to me like it could very easily be sedimentary calcium carbonate.
Really, you should test them all, but calcium carbonates tend to be white. This isn't a hard and fast rule, I have some beautiful peach and brown aragonite (one crystal form), and I think there are even some rare green ones.
Another way to test is to take two buckets of water. Put your rocks in one bucket, leave the other one without rocks as a control. After a week test to see if the pH of the bucket with rocks has changed.
As long as they won't mess up your pH you just need to clean/sanitize them, as brought up above. Driftwood should always be sanitized somehow, either boiling (the easiest/fastest), bleach (touchy, takes a long time), or saltwater (not a method I like at all). The driftwood itself is safe, the only problem is that it might leach tannins and turn your water brownish if not boiled/soaked enough...it's just all the fungi and diseases it may bring in you have to kill.
I personally have tons of driftwood, rocks, and gravel in my tanks from local rivers (and a piece of driftwood from the Pacific Ocean)...and I've never regretted using them. Just be careful to sanitize.
