Moissanite is a rare, synthetic gemstone made of silicon carbide that's often used as a diamond alternative: 

Testing

Moissanites will test positive as a diamond on most diamond testers. This is because moissanite and diamond have similar thermal conductivity properties, which most testers measure. However, there are more advanced testers available that can differentiate between the two by analyzing other properties

Moissanite has a higher refractive index than diamonds, which means it sparkles in rainbow colors when light hits it. It's also more brilliant than diamonds and has almost twice as much fire. Moissanite is durable and has a 9.5 rating on the Mohs scale. However, it's softer than diamonds and may be more prone to scratching. 

Production

Moissanite is now exclusively grown in laboratories, which reduces its environmental impact compared to naturally mined gems. 

Grading

Moissanite is graded on a scale similar to the GIA diamond color grading scale. It comes in three grades: colorless, nearly colorless, and with faint color hues.

 Visually perceive a moissanite as similar to a diamond; it has a higher refractive index, producing more rainbow 'fire' than a diamond when light hits the stone's surface. Diamonds are also physically harder than moissanite, which is 9.25 on the Mohs hardness scale compared to a diamond's rating of 10.

Moissanite is a rare synthetic gemstone made of silicon carbide, often used as an alternative to diamonds.

**Testing**  
Moissanites typically test positive as diamonds on most diamond testers. This is due to their similar thermal conductivity properties, which is what these testers measure. However, more advanced testers can differentiate between the two by analyzing additional properties.

Moissanite has a higher refractive index than diamonds, which results in a sparkling effect with rainbow colors when light strikes it. It is also more brilliant than diamonds and exhibits nearly twice as much fire. Moissanite is durable, with a hardness rating of 9.5 on the Mohs scale, but it is softer than diamonds and may be more susceptible to scratching.

**Production**  
Moissanite is now exclusively grown in laboratories, which significantly reduces its environmental impact compared to naturally mined gems.

**Grading**  
Moissanite is graded on a scale similar to the GIA diamond color grading system. It is available in three grades: colorless, nearly colorless, and with faint color hues. 

While moissanite is visually similar to diamond, its higher refractive index produces more rainbow "fire" when light hits its surface. It is important to note that diamonds are physically harder, boasting a Mohs hardness rating of 10 compared to moissanite's rating of 9.25.