Natural Ruby vs Glass Filled Ruby Beads

raw natural ruby

Natural ruby is a global favorite gemstone but glass-filled ruby? You might not have even known it existed but it does and it’s all over the jewelry and bead world. Here we will break down the differences between the two, the glass fill process, and its impact on value.

The natural ruby part is easy to understand. Natural rubies are formed deep within the Earth’s crust, over millions of years, under extreme pressure and heat. They are primarily composed of the mineral corundum, which is aluminum oxide. Trace amounts of chromium give rubies their distinct red color. Natural rubies are usually found in metamorphic rocks, such as marble, and are mined in countries like Myanmar, Thailand, and Madagascar.

What is a Glass-Filled Ruby? How to they even DO that?

Glass-filled Ruby image from Wikipedia

Glass-filled rubies are created through a man-made process that involves filling a natural ruby’s fractures with lead glass. This gemstone treatment enhances the clarity and overall appearance of lower-quality rubies, making them more visually appealing. The process was first developed in the early 2000s and has gained popularity as a cost-effective alternative to high-quality natural rubies.

Glass-filled rubies have a higher clarity than untreated natural rubies due to the filling of fractures with lead glass. This process not only improves the clarity but also intensifies the color, giving the ruby a more uniform and vibrant appearance. However, the presence of lead glass also makes these rubies more susceptible to damage from heat or chemicals, or facture. The Moh hardness of 

The Mohs hardness scale measures a mineral’s resistance to scratching. The higher the number, the harder the mineral. Rubies have a hardness of 9.0 on the Mohs scale of mineral hardness, which makes them very durable and effective for jewelry. However, glass-filled rubies have lower hardness and durability than untreated or heat-treated rubies, because the glass can be damaged by chemicals or heat. The glass may also have a different hardness than the ruby itself, which can affect the overall scratch resistance of the stone.

As for how they actually manage to fill the microscope fissures in the gemstone with molten glass…it’s a sophisticated process. This process begins with the selection of fractured or heavily included rubies which are then carefully cleaned and prepped to ensure that any dirt or impurities within the fractures are removed.


Next, the rubies are placed in a crucible containing a specialized lead glass mixture, which has a lower melting point than the rubies themselves. The crucible is then heated to a temperature between 900 and 1200 degrees Celsius, causing the lead glass to melt and infiltrate the fractures and inclusions in the rubies.

As the glass cools and solidifies, it fills the imperfections, greatly improving the clarity and color of the rubies. The final step involves polishing and cutting the treated rubies to showcase their enhanced beauty. The pink sapphire rondelles here show the color enhancing color of the process.

What is a Natural Ruby Worth to You?

ruby gemstone rough

Both natural and glass-filled rubies have their own unique characteristics, with natural rubies being more valuable and durable, while glass-filled rubies offer a more affordable alternative. Understanding the differences between these two types of rubies is essential when selecting a gemstone that aligns with your preferences and budget.

At Beadworks, we believe that each has its place but we ALWAYS disclose when a ruby or sapphire has been glass filled. Our natural ruby beads will say natural and that is reflected both in the look of the gemstone and its price. 

Unfortunately, not everyone is so scrupulous in there marketing and many, many of the rubies that you see in the marketplace, both in set-jewelry and gemstone beads, are glass filled without any notice to the consumer. 

Ways to tell Natural Ruby from Glass Filled Rubies

What are the key differences between natural and glass-filled rubies, and how can you tell them apart? 

Visual Inspection: A visual inspection can sometimes reveal differences between natural and glass-filled rubies. Glass-filled rubies may exhibit gas bubbles or a “cobweb” pattern under magnification, which are not present in natural rubies. Additionally, the color of a glass-filled ruby may appear more uniform, while natural rubies often have variations and inclusions that give them a unique character.

Specific Gravity and Refractive Index Testing: Professional gemologists use specific gravity and refractive index testing to help differentiate between natural and glass-filled rubies. Natural rubies have a higher specific gravity and refractive index than glass-filled rubies, so these tests can provide a reliable indication of the gemstone’s composition.

Gemological Laboratory Certification: To ensure the authenticity and quality of a ruby, it is recommended to purchase a gemstone with a certificate from a reputable gemological laboratory. These certificates will provide detailed information about the ruby, including whether it is natural or glass-filled, as well as information about its origin, clarity, and overall quality.

All of these aren’t available to the average consumer shopping for beads online so our ultimate guidance is 

  1. Buy from someone you can trust!
  2. If the price seems too good to be true, it is!