Here is a wonderful silver and marcasite brooch set with a good sized aquamarine, 10/16th" x 8/16th". I inherited from my aunt. It has a full English hallmark for Sydney and co, Birmingham 1913. The brooch measures 1 10/16th" x 13/16th". One tiny marcasite missing. There has been some discussion recently with regards to whether this stone is aquamarine or blue topaz. I have now been told by a local auctioneer that aquamarine when immersed in water appears to lose almost all it color and become clear whereas topaz and blue glass will still look blue. This stone is I believe aquamarine as it becomes colorless in water.