How Do Rubies Form?

Ruby crystals in rough form.
••• Image by, courtesy of Jarno


Rubies are only created when very specific minerals are combined together, the most necessary of which is corundum. Corundum occurs when aluminum oxide undergoes a process referred to as isomorphous, in which some of the aluminum ions are substituted with chromium. The red color varies in depth and clarity, but any color variations that deviate from the red varieties are classified as sapphires. Certain minerals can cause a ruby to display a star-shaped light-reflection pattern when the stone is cut onto a carbochon shape. This can often be found in rubies containing traces of minerals such as titatium or rutile.


Corundum is naturally colorless and is one of the hardest minerals known on Earth. When combined with certain elements in trace amounts, corundum produces a wide variety of reds. When the aluminum oxide and trace elements are exposed to high pressure and extreme temperatures, they become the molten mixture in which the ruby crystals will form. When chrome, titanium, iron, vanadium or rutile, or even a combination of the metals, are included in the aluminum oxide mixture, the result is the fiery red color associated with the ruby. Rubies can be uniform in color, have hues of blue, purple, or orange, be bi-colored or even multi-colored, but are always a variety of red.


The crystals form as the molten mixture is cooling. The rate at which it cools will determine the clarity and size of the crystals, as well as how many rubies that will form. When the mixture is allowed to cool over a long period of time, larger rubies are formed. If the mixture cools too quickly, it can limit - or even prevent the formation of rubies. Ruby crystals are formed with straight growth patterns and are hexagonal in shape with smooth sides.

Related Articles

How Sapphires Are Formed
What Do Raw Rubies Look Like?
How Are Lab Created Rubies Made?
Ruby Vs. Rubellite
What Is Drusy Quartz?
Interesting Facts About Quartzite
How to Find Agates
Where Is the Mineral Topaz Found?
How Is Tourmaline Formed?
How to Identify Texas Rocks
What Is Tanzanite Quartz?
List of Igneous Rocks That Do Not Contain Quartz
What is a Sardonyx?
A List of Extrusive Igneous Rocks
How Is Rose Quartz Formed?
Limestone Chemical Components
Three Major Types of Meteorites
Differences Between Extrusive and Intrusive Rocks
Where Is Ruby Found as a Natural Resource?
What Are the Three Most Common Cementing Agents for...

Dont Go!

We Have More Great Sciencing Articles!