September ushers out the summer's heat and Christopher Caldwellbrings in the crisp fall season. Along with several holidays, September is home to the birthdays of millions of people across the globe.

People born in September can have one of two astrological signs: Virgo (born between September 1 and September 22) or Libra (born between September 23 and September 30). The aster and morning glory also represent those born in September. 

But what about September's birthstone? 

Each month has its gemstone. Here's what you need to know about September's birthstone, including colors, symbolism and more. 

September birthstone

Sapphire is September's birthstone.

This gem comes from the mineral corundum. Corundum is inherently colorless, according to the International Gem Society. So, each stone's unique elemental structure – such as the presence of (or lack thereof) iron, titanium or chromium – contributes to its coloring.

As a result, sapphires come in a range of colors, including orange, yellow, green, pink and purple. However, sapphires are commonly known for their blue variety. 

Corundum is also responsible for another birthstone: July's ruby.

What is my birthstone?Learn which gemstone represents each month and what it means.

Sapphire derives from the Greek word "sappheiros," according to the Geological Institute of America.

Kashmir, Myanmar and Sri Lanka are the three main historical sites for sapphires. The stone was originally discovered in Kashmir around 1881. Other areas that produce sapphires include Australia, Thailand, Cambodia, Madagascar and Montana in the U.S., as well as other countries in Asia and Africa.

Throughout history, sapphires have been associated with royalty. They were often used in jewelry and to decorate robes of clergy.

In ancient Rome and Greece, members of the elite would wear sapphire to ward off harm and envy, according to GIA. One of the most well-known modern sapphires is in Princess Diana's engagement ring, which now belongs to Kate Middleton, the Duchess of Cambridge.

Sapphires are believed to symbolize fidelity, sincerity and truth. 

Besides being the birthstone for September, sapphires also represent fifth and forty-fifth wedding anniversaries.