Moissanite is a gemstone originally discovered in a meteor crater. So it's literally a space rock.
Moissanite looks a lot like a diamond. They're both clear and sparkly. But moissanite is not a fake diamond and shouldn't be thought as one. It's a beautiful gemstone in its own right.
Because of how much a moissanite looks like a diamond, it has become the most popular diamond alternative.
Moissanites are also great because they're completely earth-friendly and conflict-free. Since moissanite is developed in a controlled lab, there's no mining involved or harm to the environment.
Moissanite is the most popular diamond alternative for couples on a budget. Most people can't see the difference between the two.
Both moissanites and diamonds make beautiful engagement rings. With either option, you'll reap these benefits:
     Durability: Moissanite rates 9.25 on the Mohs Scale of Hardness. It's second only to diamonds (which have a rating of 10). They're both hard enough for everyday wear, and won't scratch or break easily.
     Sparkle: Both are beloved for their beautiful sparkles. But some astute observers can tell a difference. Moissanites usually have more of a rainbow sparkle, while diamonds emit a combination of colorless sparkle, rainbow sparkle, and flashes of light. Both are beautiful. What you like is your personal choice. 
     Cut: Both diamonds and moissanites are available in a variety of shapes. But round is the most popular for both choices. The round brilliant cut offers the most sparkle and appears the most white. 
Wondering if you can tell the difference between moissanite and a diamond? There is very little difference visually. In fact, moissanite has a higher refractive index so it's even more sparkly than a diamond. 

You may prefer moissanites to diamonds for the following reasons:
  • They are lot less expensive than diamonds: A quick search online at the time of writing revealed that an average 1 carat diamond costs upwards of $4000, with the average cost of a diamond engagement ring being $5000. A moissanite of similar appearance and size can cost up to 90% less than a diamond, with a 1 carat moissanite only setting you back about $400.
  • Extreme brilliance: Moissanites are very sparkly. They have a high refractive index. This creates a greater sparkle than that of a diamond. The sparkles are often rainbow colored rather than colorless. In short, you get a flashy ring. 
  • Better clarity: Moissanites are not sold unless the clarity grade is VS or above. This grade means that there are no visible flaws. Diamonds, on the other hand, can have flaws that can be seen with the naked eye. 
  • Ethically created: Unless you know how to find a conflict-free diamond, real diamond could have blood on it. Even if it doesn't, it could be mined from somewhere with unfair labor practices and unsafe working conditions.   Unlike diamonds, moissanites aren't mined from the Earth.  Moissanite is grown in a controlled lab environment. This eliminates the worry of unfair labor practices and warfare. They also have a smaller carbon footprint. All of these reasons make moissanites an eco-friendly choice for an engagement ring.
1) Is moissanite as good as a diamond?
Moissanite has properties very close to diamonds. Moissanite scores 9.25 on the Mohs Scale of Hardness. That makes it the hardest gemstone used in jewelry next to diamonds (which is a 10). Sparkle wise, moissanite has an even higher refractive index than diamonds, so it's even sparklier than a diamond. But it has more of a rainbow sparkle, whereas diamonds has both white and rainbow. Moissanite can also resist heat just as well as diamonds. 
In short - moissanite is a beautiful, brilliant stone that will hold up to everyday wear.
If asking whether moissanite is good enough for your engagement ring, that's up to personal preference. Some girls love the savings and the intense sparkle, while others only want a real diamond.
2) Can you tell the difference between a diamond and moissanite?
Most people cannot tell that a moissanite is not a diamond. Maybe if you had the two side by side, a very keen observer can see that they are slightly different. Maybe you can see that the moissanite has more rainbow sparkles. Or that they have different casts of color under different lighting conditions. But even then, the casual person may not be able to say which one is which. In fact, even professionals have a hard time telling them apart, unless they use a special moissanite tester. 
3) Do moissanite rings last?
Yes, just like diamonds, a moissanite stone will last for the rest of your life. It is very durable and will hold up to everyday wear and tear. Moissanite will also not lose brilliance or get cloudy over time. Just make sure you choose a durable setting as well in gold or platinum (like you would with a diamond). Don't use sterling silver plated in gold or platinum. That is not sturdy enough to last.
4) What is the best fake diamond to buy?
Moissanite is closest to a diamond in terms of durability and brilliance. But please don't think of moissanite as a "fake diamond." It is a REAL gemstone that just happens to look a lot like diamonds. The fact that it's just a fraction of the cost is a huge plus.