Topaz is the birthstone for November and comes in a variety of colors, most popular color is blue. The color can range from light, medium and a dark tone. the yellow variety is known as Imperial and can be very valuable as to its rarity. Measuring 8 on Mohs hardness scale, Topaz is very durable. Topaz is said to be soothing stone said to calm tempers and cure madness and nightmares. Topaz is the astrological stone for Leo and Sagittarius.