Request #300 From Matilda

 I know it’s a long shot but I’ve been trying to find the name of this book since I was very young. For some reason it just completely evades me! 

I can describe the cover. It was deep red and there was some form of emerald jewel on it. There is some sort of link to an emerald stone. I just can’t remember what it is. I’m almost certain the book is set somewhere like Russia. It’s about a girl who is separated for her mother and her name MAY be Anastasia but it’s all hazy! 

Please let me know if you have any idea what it is as I would love to read it again, it was one of my favourites when I was young! 
P.S. I appreciate the information I have given is very sparse. I’ve done my own research and it’s never achieved any results, but I thought it might be worth a shot to ask you!