I have read a fair bit about all of these. Please read the article if interested and then let me know what you think of my conclusions:

http://socyberty.com/paranormal/mysterious-and-strange-archaeology-discoveries-that-science-cannot-explain/

My thoughts:

• I think 1,2 and 10,11 are significant mysteries.
• I think 3 and  4,8,9, 12  are interesting but not overly mysterious. 
• I think 5, 6 and 7 are either astoundingly mysterious or mysterious hoaxes.
• A mystery is a mysterious hoax if even if you accept that it is a hoax there remains a signifigant mystery to be solved. I figure this term belongs to Gerald Hawkins. Even if a hoax, there is a significant mystery to be solved, eg as with crop circle theorems).
• A mystery is astounding if it's truth challenges a paradigm. For example, finding cocaine in an Egyptian is astounding.