Beryl over , and its dimensions were long and in diameter. The largest cut aquamarine gem is the Dom Pedro aquamarine, now housed in the Smithsonian Institution's National Museum of Natural History. The ancient Romans believed that aquamarine would protect against any dangers while travelling at sea, and that it provided energy and cured laziness. Emerald is green beryl, colored by trace amounts of chromium and sometimes vanadium. Most emeralds are highly included, so their brittleness (resistance to breakage) is classified as generally poor. The modern English word "emerald" comes via Middle English "Emeraude", imported from modern French via Old French
Gemstone value of the stone. Some treatments are used widely because the resulting gem is stable, while others are not accepted most commonly because the gem color is unstable and may revert to the original tone. Heat can improve gemstone color or clarity. The heating process has been well known to gem miners and cutters for centuries, and in many stone types heating is a common practice. Most citrine is made by heating amethyst, and partial heating with a strong gradient results in “ametrine” – a stone partly amethyst and partly citrine. Aquamarine is often heated to remove yellow tones, or