This is a K18 cross pendant. I don't know the type of blue stone. Please check the photos carefully and only purchase if you agree. ◎Notes on Transactions◎ 1. About the condition of the items Most of the items for sale are old or vintage. There may be stains, tears, wear, scratches, and other damage that are difficult to see in the images. If you are concerned about the condition or authenticity of the item, please refrain from purchasing. 2. About returns Due to the nature of the items, cancellations, inquiries after purchase, claims, and returns are not accepted. Thank you for your understanding.