Aquamarine is a blue to green-blue gem-quality variety of beryl. The beryl group of gemstones is most famous for chromium-rich green emerald, one of the ‘precious four’ gems (diamond, sapphire and ruby are the remaining three). Aquamarine is an official birthstone for those born in March. Aquamarine is exceptionally hard and has an outstanding vitreous glass-like luster. It is most famous for its breathtaking sea-blue colors which can range from pale light blue to medium-dark blue. The name ‘aquamarine’ was derived from an old Latin expression which meant ‘seawater’.
Aquamarine and emerald belong to the same family, but they are surprisingly different. Aquamarine and emerald are both beryllium aluminum silicates, but emerald is colored by trace amounts of chromium (and sometimes vanadium), while aquamarine obtains its color from iron impurities within colorless beryl (goshenite). Aquamarine and emerald have essentially the same specific gravity and refractive index, but emerald tends to be hazy and full of inclusions, while aquamarine is known to occur with excellent transparency and clarity.
Aquamarine, and other types of beryl are quite durable and hard, ranging from 7.5 to 8 on the Mohs scale of mineral hardness. A dark and deeply saturated blue is the most desirable and valuable aquamarine color.
