Gemstone Ruby Facts

There are only four precious gems. These are diamond, sapphire, emerald and ruby. Ruby's official name is aluminum oxide. Some people refer to the ruby as the red sapphire. The ruby is in the red corundum family. Though rubies can be found throughout the world, certain locations produce rubies of a higher value.

The element, chromium, is what makes a ruby red. The only stone harder than a ruby is a diamond. On the Moh's Hardness Scale, ruby has a score of 9 (out of 10). Most naturally produced rubies have flaws of other colors. These are called inclusions. Some inclusions add beauty to the stone, while others take away from a ruby's value.

There is no color-grading system used for gemstones like the one that is used for determining diamond value.

Ruby's color or hue varies in graduation:

• red to slight orange
• to strong orange
• to slight purple
• to strong purple

Red is considered the ideal hue for a ruby.

Color saturation ranges as follows:

• "Vivid" (bright red)
• "Weak" (light pink)

Most natural rubies have tiny areas of gray or black called "extinction." The fewer extinctions, the more valuable the ruby. Lighter, shallower rubies usually have the fewest areas of extinction.

Natural rubies form as flat, wide crystals. This makes the ruby more difficult to facet because it is hard to find a ruby that is deep. Usually 60 percent of the stone is cut away when the ruby cutter is creating its facets.

Manmade rubies have bright, vivid clarity. They are very popular because they are less expensive than mined rubies. Manmade rubies have less inclusions than natural rubies. Another name for manmade rubies is "lab" rubies.

Most natural rubies are heated to sharpen their color and clarity. Heating can often correct inclusions. It is a legal process and gemologists have been heating rubies for thousands of years. Heating a natural ruby actually increases a ruby's value.

Another treatment performed on mined rubies is heating the stone, melting away the flaws and filling the space with melted glass. This is not considered permanent, nor is it an accepted practice