Rubies and Sapphires

Definition

Rubies and sapphires are both varieties of the mineral corundum, known for their vibrant colors and use as gemstones. The primary difference between them lies in their color; rubies are red due to the presence of chromium, while sapphires can be found in a variety of colors, with blue being the most popular, attributed to iron and titanium. Both stones are formed under specific conditions in the Earth’s crust, often involving metamorphic processes and can be significantly influenced by metasomatism, where the chemical composition of a rock changes due to fluid interactions.

5 Must Know Facts For Your Next Test

1. Rubies and sapphires are both classified as precious stones, making them highly sought after for jewelry.
2. The formation of rubies and sapphires can occur in metamorphic rocks and alluvial deposits, often linked to regional or contact metamorphism.
3. The value of rubies is typically higher than that of sapphires, especially when it comes to deep red rubies known as 'pigeon's blood.'
4. Both gems can undergo heat treatment to enhance their color and clarity, a common practice in the gemstone industry.
5. Natural rubies and sapphires can contain inclusions, which are imperfections that can affect their value; however, some inclusions may enhance their character.

Review Questions

• How do rubies and sapphires differ in their chemical composition and physical properties?
  • Rubies and sapphires both originate from corundum but differ primarily in color due to their chemical compositions. Rubies are red because of chromium impurities, while sapphires exhibit various colors depending on the presence of other elements like iron and titanium. These differences not only influence their aesthetic appeal but also affect their market value and desirability in gemology.
• Discuss the role of metasomatism in the formation of rubies and sapphires within geological contexts.
  • Metasomatism plays a crucial role in the formation of rubies and sapphires by altering existing rock compositions through the introduction of chemically active fluids. These fluids can enhance or change the mineral content in rocks under high pressure and temperature conditions, leading to the crystallization of corundum. The specific conditions during metasomatism determine whether corundum forms as rubies or sapphires, highlighting how geological processes directly influence gem characteristics.
• Evaluate the impact of human intervention, such as heat treatment, on the properties and market value of rubies and sapphires.
  • Human intervention through methods like heat treatment significantly impacts both the properties and market value of rubies and sapphires. Heat treatment can enhance color intensity and clarity, making these stones more appealing to consumers. However, while treated stones may still retain considerable value, they typically sell for less than untreated stones due to concerns about authenticity and natural origin. This dynamic illustrates how human practices intersect with geological processes in determining gemstone valuation.

Related terms

Metasomatism: The process through which the chemical composition of a rock changes due to the introduction of fluids that alter its mineral content.

Corundum: A crystalline form of aluminum oxide that serves as the parent mineral for rubies and sapphires.

Gemology: The science of studying gemstones, including their formation, properties, and valuation.