We use mostly solid 14kt gold for our jewelry.
We use some 10 karat gold or sterling silver due to the very high gold price. 
We use no gold plate or gold filled materials!
FYI: Gold filled does NOT mean "Filled with gold"
In fact it is just about the opposite....what it really means is heavy gold plate.
It's generally filled with brass or steel!
We actually make 99.95% of our gemstones!
Take a look at our "Factory Pictures" page!
I think we are the only company in the USA to actually do this!
We make Synthetic, Man-Made, (Lab Made)
Rubies and Sapphires.
They are chemically and physically identical to something nature made, i.e., our Shelby "Rubies and Sapphires" are chemically & physically the same as those dug from the ground, with THIS EXCEPTION: since we made them, most are nearly flawless because we control the ingredients and cooking temperature. It is rare to find a flawless natural gem, and if you are lucky enough to find one they are VERY expensive.
We make the very rare (in Nature) fancy colored sapphires such as:
GoldPink ChampagneAqua BlueYellow,
and the traditional Dark Blue Sapphire.
We make Simulations of Diamonds, Emeralds, Aquamarine,
Blue Topaz, Amethyst, etc...
We have decided to call our Shelby Simulated Diamonds 
"Diamond Encore™" 
because it will make them easier to search for on the internet!
Diamond Encore™ is chemically different from a genuine diamond.
Diamond Encore™ contains NO Carbon. 
Genuine diamonds are basically pure carbon. 
There are 3 basic forms of carbon.....the soot  from a candle, graphite,
(if you heat the soot very strongly it will turn into graphite). If you heat the graphite strongly and compress it VERY strongly, it forms diamond. That's why many diamonds contains little black spots....sometimes the graphite doesn't completely change to diamond. 
Diamond Encore™ is visually indistinguishable from a very good genuine diamond. Diamond Encore™ can scratch glass easily just like a natural diamond can. 
By the way, if you purchase a Diamond Encore™ and it gets accidentally scratched, we'll replace it at no charge for the gem.
The only natural substance able to scratch a Diamond Encore™ is a natural diamond or sapphire. Over the years, we have replaced a few scratched stones, but generally they have been scratched by nail files that were covered with natural diamond chips.
Shelby "Emeralds", "Aquamarines", "Amethyst", "Citrine", and "Topaz" are also chemically different from their natural counterparts.
They look like the very best natural gems but our gems are about 40% harder and considerably tougher than those fragile natural gems.
Our simulated gems generally are much, much better than natural gems!