Alexandrite is a rare and captivating gemstone, celebrated for its remarkable ability to change color depending on the light source. This unique optical phenomenon makes it highly sought after for fine jewelry and collectors. Understanding the physical strength of alexandrite is important for both appreciating its qualities and ensuring its longevity in various applications. Examining its inherent properties provides insight into how it withstands daily wear and maintains its beauty over time.
Understanding Alexandrite’s Hardness
Mineral hardness refers to a gemstone’s resistance to scratching, measured by the Mohs scale of mineral hardness. This scale ranges from 1 (softest, like talc) to 10 (hardest, like diamond). Alexandrite ranks at an 8.5 on the Mohs scale, indicating a high level of scratch resistance. This places alexandrite among the more durable gemstones for everyday wear.
For comparison, diamond, the hardest known mineral, is a 10, while sapphire and ruby are both 9. Common household dust and quartz register around 7. While alexandrite is highly resistant to scratches from most common materials, it can still be scratched by harder gems like sapphire, ruby, or diamond.
Alexandrite’s Toughness and Overall Durability
Beyond hardness, a gemstone’s toughness describes its resistance to breaking, chipping, or fracturing when subjected to impact or pressure. Alexandrite exhibits good to excellent toughness, meaning it is less prone to shattering. Alexandrite possesses no cleavage, which means it lacks preferred planes along which it could easily split. This absence of cleavage enhances its structural integrity.
When alexandrite does break under extreme force, it typically exhibits a conchoidal fracture, producing smooth, curved surfaces similar to broken glass. Furthermore, alexandrite demonstrates good stability, being resistant to damage from heat, light, and common chemicals found in household cleaning products.
Factors Affecting Alexandrite’s Resilience
The overall resilience of an individual alexandrite gemstone can be influenced by several internal and external factors. Inclusions, which are internal characteristics like tiny crystals, gas bubbles, or fractures within the stone, can affect its durability. Significant or numerous inclusions can create weak points, potentially making the stone more susceptible to chipping or breaking under impact.
While rare for alexandrite, some gemstones undergo treatments to enhance their appearance, which can sometimes impact their strength. However, alexandrite is not typically subjected to treatments that would compromise its inherent durability. The way a gemstone is cut also plays a role in its resilience. Cuts with sharp corners, pointed facets, or very thin girdles (the perimeter of the stone) can make a stone more vulnerable to chipping or breakage, regardless of its inherent properties.
Practical Care for Alexandrite
Maintaining alexandrite’s strength and beauty requires attention to practical care. It is advisable to avoid wearing alexandrite jewelry during activities that might expose it to harsh impacts or abrasive surfaces.
Storing alexandrite pieces separately from harder gemstones, such as diamonds or sapphires, prevents potential scratching. Using a soft pouch or a separate compartment in a jewelry box helps protect its surface.
For cleaning, warm, soapy water and a soft brush are generally safe and effective for alexandrite. While ultrasonic cleaners are often considered safe for alexandrite, caution is advised for stones with inclusions. Exposure to harsh chemicals, including strong acids or bleaches, should be avoided as they could potentially damage the stone’s surface polish over time.