Before the 20th century, all gems in the brown, orange, and yellow colour range were called topaz. Modern gemology was only recognized as a science in the 1930s. Today we know that topaz and brown quartz are actually two different gemstones. Citrine is less likely to be confused with Topaz today, but it does happen.
Nearly all Aquamarines on the market have been heat treated to enhance the colour. In meeting with the consumer preference for aquamarines in deep blue, the stones are heated near 800 degrees Fahrenheit, which causes the blue colour to emerge and the yellow/green tones to disappear. As a gemstone, they work equally beautifully set in silver or gold. Many aquamarine stones are virtually free of inclusions and their lustre is vitreous or glass-like.