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What Is the Density of a Ruby?

Rubies are one of the most well-known precious gemstones, with references in history dating to the Bible and ancient Sanskrit writings. Rubies are a corundum, a family of minerals that also includes the many different colors of sapphire. In fact, a ruby is nothing more than a red sapphire. The only difference between them is the type of chemical inclusion that gives them their colors.

Density of Ruby
- Mineral density is referred to as specific gravity, and it's useful to know in case you need to identify a particular mineral without being able to test it in a laboratory setting. Ruby is a 4 on the density scale, which is slightly above average from other minerals. The specific gravity refers to how dense the ruby is compared to water.
Scientific Composition of Rubies
- Ruby is one of the hardest minerals on the planet, coming in only behind diamond and a few others. Ruby is a 9 on the Moh scale. Testing of a ruby with this scale requires you to have minerals on hand with known hardness levels. If a mineral can scratch a ruby, it's higher on the Moh scale. If it can't scratch the ruby, it's lower. A ruby's index of refraction is 1.75, which can be used as another way to determine the type of mineral by seeing the way the light is bent when it hits the mineral.
Unique Characterisitics of Rubies
- Rubies are very unique by being the second-hardest mineral, and they are also one of the few that can be used in laser applications. The red that differentiates them from others in their family of minerals comes from the element chromium. A ruby's melting point is noteworthy as well at 2,044 degrees C.
Methods of Calculating Ruby Density
- The primary method for determining the density of a ruby uses water and a ruby. The density of the water is divided from the density of the ruby, and this gives a quick and relatively painless way of figuring out the density--along with being useful in figuring out what an unknown mineral could be. Ruby's specific gravity is 4, which means it is four times the density of water. All you need is a sensitive enough scale to calculate specific gravity in your own home.
Where Rubies are Formed
- Thailand, Cambodia and Afghanistan are the sites for most ruby mining throughout the years. There are a few sources in the United States, but there is not much ruby volume in those. Corundum, which is the mineral that forms ruby, can be found in many different types of rock. Mica schist and marbles are the most common formations to find rubies and sapphires, but you can sometimes find them in pegmatites.

Rocks & Minerals