# Question: What is refractive index in gemstones?

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The refractive index of a gemstone provides the single most important piece of information to a gemologist seeking to identify an unknown stone. It is a constant that is measurable to four significant figures (i.e. 3 decimal points) and can allow gems to be distinguished even when their R.I’s differ only very slightly.

## What is the most refractive gem?

This is the term used when identifying gems. It is another way of describing the amount of refraction that will occur when a ray of light enters a substance. The refractive index of a material is a number which ranges between 1.00 and 2.42. Diamond has the highest refractive index of all: 2.42.

## What is refractive index in gemology?

The index of refraction or refractive index equals the ratio between the velocity of light in the two media. The first medium, usually air, sets the unity light velocity (1). The refractive index then becomes 1/v, where v is the velocity of light in the denser medium.

## What gemstones are double refractive?

Double refraction is when a ray of light passes through the gemstone, is slowed, bent, and split in two. Sapphire is a double refractive material as well, as are peridot, tourmaline, and zircon.

## What is a good refractive index?

Refractive Indices and Double Refraction Values

Gemstone Refractive Index Double Refraction
Ruby (corundum) 1.762-1.778 0.008
Sapphire (corundum) 1.762-1.778 0.008
Benitoite 1.757-1.804 0.047
Shattuckite 1.752-1.815 0.063
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## What makes a gem brilliant?

The Basics Of Gemstone Brilliance

The brilliance of a gemstone is determined by the path light takes as it travels through the stone. … Only those light rays that reflect back out through the crown of the gemstone toward the eye of the viewer provide brightness and color. These rays account for a gemstone’s brilliance.

## What is refractive index of sapphire?

Some gemstones are singly refractive; they have only one refractive index. Other gemstones – in fact, most – are doubly refractive; they have two different refractive indices.

## What is the highest refractive index?

The highest refractive index is of Diamond with its value 2.42.

• Refractive index of glass is 1.5.
• Refractive index of water is 1.33.
• Refractive index of ruby is 1.77.