Heart and chain are Sterling Silver. Black stone is in silver plated metal. Rowing heart measures ~8mm. Chain is cable link 1.5mm thick 18 inches long with spring ring clasp. Black stone (faceted) is 15mm from top of cap to point of stone, 10mm wide, overall black stone pendant with bail is 3/4 inch long. 

Chain and heart can be cleaned with baking soda (rub it dry).