What is the difference between cubic zirconium and Moissanite?   

Moissanite and cubic zirconium have very little in common except that they are commonly compared because they are both categorized as "diamond simulants" or "artificial diamonds."    The biggest and most important difference is that cubic zirconium is soft.  The reason cubic zirconium becomes dull and appears clouded is because it can be scratched during routine wear.  The scratches are responsible for making a cubic zirconium stone look like a piece of salt rock over time. 

Moissanite, on the other hand, is second in hardness only to diamond.  In fact, the only thing that can scratch a Moissanite is another Moissanite or a diamond.  That's it.    So the Moissanite stone you buy today, regardless of who you buy it from, is guaranteed to look as brilliant and clear 50 years from the day you bought it.  

How can I be sure that I am purchasing Moissanite? 

All jewelers who sell Moissanite are required to provide a Charles & Colvard Certificate of Authenticity with all of the stones they sell.  I would suggest you make sure that this will be included with your order, along with a guarantee offered by the actual jeweler.  My guarantee provides for a full refund if my customer is not happy with the stone(s) for whatever reason.  I ask that the stone(s) be returned to me within ten days of the date that my customer receives the order.  If this is not possible, I ask that my customer give me a call to let me know the stone will be returned so that I can know when to expect it.     

How is Moissanite graded? 

Moissanite is not separated into grades because its manufacturer has set specifications that each stone must meet before being released to distributors. Those specifications are comparable to diamonds which have been graded VSI (Very Slightly Included - Minor inclusions difficult to locate at 10x).  All Moissanite stones are manufactured in the same laboratory at Charles & Colvard and, contrary to some advertising I've seen on the internet, a jeweler cannot purchase either Moissanite rejects or Moissanite jewels that are said to be superior to other Moissanite jewels. The Moissanite jewels I sell are the same jewels you find in physical stores but I don't have the overhead so I can sell for less. 

Can I get a Moissanite stone which is comparable to a colorless diamond?  

The color of Moissanite stones can and do vary -- anywhere from G through J on the diamond color grading scale.   Color is the biggest concern and complaint that I receive from my customers.  I'm sure this is because everybody wants a completely colorless stone but even completely colorless diamonds are rare and very, very expensive.   You will not find a completely colorless Moissanite stone.   Some people see a yellow cast to Moissanite stones and others see a green cast.  I've seen a green cast but can't say I've ever seen a yellow cast.   In its primitive state, Moissanite is green and I suspect that Charles & Colvard will one day perfect the process of producing a perfectly colorless stone.  Unlike diamond, Moissanite does not increase in price with increased absence of color.

Most diamonds you see in jewelry stores fall into the diamond color G category and really cannot easily be differentiated from Moissanite.  Most jewelers do not keep many truly colorless diamonds in their inventory because of the enormous expense.  

Can I purchase a Moissanite stone based on its carat weight?

Moissanite is lighter in weight than diamond so when you are dealing with Moissanite, it is better to refer to it only in millimeters. 
 
This means that if you have a 3 carat diamond, which follows the accepted diamond dimension requirements below, and an identical Moissanite stone, the Moissanite is not going to weigh 3 carats.  It is going to weigh approximately 2.72 carats.  The physical size is the same.  The weight is different.  This is why its best to refer to Moissanite in terms of millimeters. 
 
Moissanite stones have virtually the same dimension requirements set by the diamond industry for optimal reflection of light.   This is a mathematical formula based on the depth and diameter of the stone.  Moissanite stones fall within the optimal parameters.