QUESTION: I just bought two 'gem silica' stones that looked exactly like quantum quattro silica. Are they one in the same? If not, what is gem silica? What's it comprised of? It looked just like quantum.
MY ANSWER: Gem silica is chrysocolla in quartz. The highest grades are completely embedded in the quartz so you get a very uniform blue. In most cases, though, there are other minerals included, often malachite or other blue or green minerals. That's because chrysocolla is a copper mineral, and so are most other bright blue and bright green minerals. Quantum Quattro Silica is a very specific combination of minerals found only in Namibia -- chrysocolla, shattuckite, malachite, dioptase, and smoky quartz. The shattuckite is rare, as is the dioptase, so it's unlikely that the gem silica you have would be quantum, although I have occasionally seen people sell quantum as gem silica, so it's possible. Quantum can be considered a type of gem silica with inclusions (the shattuckite, malachite, and dioptase), though. Hopefully that makes it all clearer than mud.
Orignally posted at CrystalsAndJewelry.com June 2004, Updated January 2013