What is the difference between a Blue Topaz, and an Aquamarine?

Answer 1

Aquamarine is the blue or blue-green member of the beryl family and is ranked 7.5 to 8 on the Mohs' scale. The colors of aquamarine range from the lightest blue of the sky to the deepest blue of the sea, hence the name, but the most valuable are those aquamarines deepest in tone and color saturation. Women all over the world love aquamarine because its color suits almost any complexion or eye color. Aquamarine is the traditional birthstone for March.
The name "topaz" likely originated from Topazos, an ancient Red Sea island. Topaz can be yellow, orange, light to dark blue, pink-red, red, violet, light green, and colorless. Some are enhanced with colorful treatments to create special effects. On Mohs' hardness scale, topaz is a tough 8. Sources include Brazil (Minas Gerais), Afghanistan, Australia, Myanmar (Burma), China, Japan, Madagascar, Mexico, Namibia, Nigeria, Pakistan, Russia (Urals, Transbaikalia), Zimbabwe, Sri Lanka, and the U.S.

Answer 2

Blue topaz is a blue-colored aluminum fluorsilicate. Aquamarine is a blue-colored beryllium aluminum silicate. Topaz is a nesosilicate, where individual silicon-oxygen tetrahedra are not connected while beryl is a cyclosilicate, where silicon-oxygen tetrahedra link up into six member rings.