You might be surprised to learn that the blue color that springs to mind for topaz is hardly ever natural: It’s almost always caused by treatment. In fact, topaz has many colors to offer gem lovers, including pinks and purples that rival fancy sapphire!
Topaz is allochromatic. Its color is caused by impurity elements or defects in its crystal structure rather than by an element of its basic chemical composition. Chromium causes natural pink, red, and violet-to-purple colors in topaz. Imperfections at the atomic level in topaz crystal structure can cause yellow, brown, and blue color. Brown is a common topaz color, and is sometimes mistakenly called “smoky quartz.”
Citrine is very rare in nature. It used to be confused with topaz. Today, its durability and affordability makes it the top-selling yellow-to-orange gem. Citrine’s most popular shade is an earthy, deep, brownish or reddish orange.
Most citrine quartz available now is the result of heat treatment of amethyst quartz. Based on the gems from the Victorian era that have surfaced, it’s not hard to imagine that citrine was treasured even in earlier times.