== deletion valid reference on gemstone page == 

 Hi  

 You deleted a reference I've been using on and off for years. According to Wikipedia guidelines point 3): "online textbooks" the reference is in fact according wikipedia linking guidelines. The page shows over 100 full text copyright-free (antique) scientific publications on gemological topics and is furthermore a non-commercial page, without and advertisements. The reference I am referring to is tThis library page 

 Unless you have a valid reason to delete the reference I will be placing it back. I would furthermore appreciate it if you would contact me before deleting references I add. I am take great care in the sources I use.  

 Thank you.