Rubellite, a term often used in the jewelry industry, refers to a pink to red variety of tourmaline. Tourmalines are boron silicate minerals that belong to a complex group with a wide range of chemical compositions. The color of rubellite can vary from vivid pink to deep purplish-red, and it is highly prized for its intense coloration. Rubellite is not only valued for its aesthetic appeal but also for its hardness, which contributes to its durability and suitability for use in various types of jewelry.
What is Hardness?
Hardness is a measure of how resistant a material is to being scratched or abraded. In the context of gemstones, hardness is one of the most important physical properties, as it determines the stone’s ability to withstand daily wear and tear without sustaining damage. The concept of hardness is particularly relevant when considering the longevity and maintenance of gemstone jewelry.
The Mohs Scale of Hardness
To evaluate and compare the hardness of different materials, including gemstones, scientists and jewelers use the Mohs scale of hardness, named after the German geologist Friedrich Mohs who introduced it in 1812. This scale ranges from 1 (softest) to 10 (hardest), with each number representing a specific mineral that serves as a reference point. For example, talc is rated at 1, while diamond, the hardest known natural material, is rated at 10.
The Mohs scale is not linear; the difference between each level is not uniform. For instance, the difference in hardness between corundum (9) and diamond (10) is significantly greater than the difference between any other two adjacent levels on the scale.
Rubellite Hardness on the Mohs Scale
On the Mohs scale, rubellite has a hardness rating of 7 to 7.5. This means that rubellite is relatively hard and durable, making it suitable for use in jewelry. However, it is not as hard as some other popular gemstones, such as sapphire (9) or diamond (10). Despite this, rubellite’s hardness is still sufficient to resist scratches from many common substances, including dust and sand, which are typically composed of quartz (7).
Comparison with Other Gemstones
To better understand where rubellite stands in terms of hardness, let’s compare it with some other well-known gemstones:
- Diamond (10): The hardest natural material known, diamond is virtually scratch-proof. It is the ideal choice for engagement rings and other pieces of jewelry that are worn daily.
- Sapphire (9): Sapphire is second only to diamond in terms of hardness. It is highly resistant to scratches and is a popular choice for rings and other jewelry items.
- Emerald (7.5 to 8): Emerald is slightly harder than rubellite, but it is more prone to fractures due to internal inclusions. Therefore, despite its higher hardness, emerald requires more careful handling.
- Quartz (7): Quartz, which includes varieties like amethyst and citrine, has the same hardness as the lower end of rubellite’s range. It is durable enough for most jewelry applications but may be susceptible to scratches over time.
- Corundum (9): Corundum, which includes ruby and sapphire, is much harder than rubellite. It is highly resistant to scratches and is often used in high-end jewelry.
- Topaz (8): Topaz is harder than rubellite and is also very durable. However, it can be brittle and may chip if struck sharply.
- Garnet (6.5 to 7.5): Garnet’s hardness can overlap with rubellite’s, depending on the specific variety. It is generally durable but may be more susceptible to scratches than rubellite.
Implications of Rubellite’s Hardness
While rubellite’s hardness of 7 to 7.5 is respectable, it does come with certain implications for its use in jewelry:
- Durability: Rubellite is durable enough to be used in rings, pendants, earrings, and other types of jewelry. However, it is not as durable as sapphire or diamond, so it may require more care, especially in settings where it is exposed to frequent contact with other surfaces.
- Scratch Resistance: Rubellite can resist scratches from most everyday materials, but it is still vulnerable to scratches from harder substances, such as quartz, topaz, and corundum. Therefore, it is important to store rubellite jewelry separately from other gemstones to prevent damage.
- Polishing and Maintenance: Due to its moderate hardness, rubellite can be polished to a high luster, enhancing its beauty. However, over time, the surface may develop fine scratches, especially if the jewelry is worn frequently. Regular cleaning and occasional repolishing can help maintain the gemstone’s appearance.
- Setting Considerations: When designing jewelry with rubellite, it is important to choose a setting that provides adequate protection for the gemstone. Prong settings, bezel settings, and channel settings can all help shield the stone from direct impact and reduce the risk of chipping or scratching.
Factors Affecting Rubellite Hardness
While the Mohs scale provides a general guideline for assessing hardness, several factors can influence the actual hardness of a rubellite specimen:
Chemical Composition
Rubellite is a type of elbaite, which is a member of the tourmaline group. The chemical composition of rubellite can vary depending on the presence of trace elements such as lithium, magnesium, iron, and manganese. These elements can affect the crystal structure of the gemstone, potentially influencing its hardness. For example, rubellites with higher concentrations of lithium may exhibit slightly different hardness properties compared to those with more iron or manganese.
Crystal Structure
The arrangement of atoms within a gemstone’s crystal structure plays a crucial role in determining its hardness. Tourmaline, including rubellite, has a trigonal crystal system, which means that its atoms are arranged in a hexagonal pattern. This structure contributes to the gemstone’s overall durability, but it can also create areas of weakness along certain planes. As a result, rubellite may be more susceptible to cleavage or fracturing along these planes, even though its overall hardness is relatively high.
Inclusions
Like many gemstones, rubellite can contain inclusions, which are internal or external imperfections that form during the gemstone’s growth. Inclusions can weaken the structure of the gemstone, making it more prone to chipping or breaking. Common inclusions in rubellite include needles, tubes, and liquid-filled cavities. While small inclusions are usually harmless, larger or more numerous inclusions can compromise the gemstone’s integrity and reduce its hardness.
Heat Treatment
Some rubellite specimens undergo heat treatment to enhance their color or clarity. Heat treatment can affect the gemstone’s internal structure, potentially altering its hardness. In most cases, heat treatment does not significantly change the hardness of rubellite, but it can make the gemstone more sensitive to thermal shock. Therefore, it is important to handle heat-treated rubellite with care, especially when exposing it to extreme temperature changes.
Environmental Factors
Environmental factors, such as exposure to chemicals, humidity, and temperature fluctuations, can also impact the hardness of rubellite over time. For example, prolonged exposure to acidic substances can cause the gemstone to deteriorate, reducing its hardness and increasing its vulnerability to damage. Similarly, extreme temperature changes can cause thermal expansion and contraction, leading to stress fractures within the gemstone.
Caring for Rubellite Jewelry
Given rubellite’s hardness of 7 to 7.5, proper care and maintenance are essential to ensure the longevity of your jewelry. Here are some tips for caring for rubellite:
Cleaning
- Use Mild Soap and Water: To clean rubellite jewelry, gently wash it with mild soap and warm water. Avoid using harsh chemicals or abrasive cleaners, as they can damage the surface of the gemstone.
- Ultrasonic Cleaners: Ultrasonic cleaners can be used to clean rubellite, but it is important to exercise caution. If the gemstone contains inclusions or has been treated, ultrasonic cleaning may cause damage. Always consult with a professional jeweler before using an ultrasonic cleaner on rubellite jewelry.
- Steam Cleaners: Steam cleaners are generally not recommended for rubellite, as the high temperatures can cause thermal shock and lead to cracking or fracturing.
Storage
- Store Separately: To prevent scratches, store rubellite jewelry in a separate compartment or pouch within your jewelry box. Avoid storing it with harder gemstones, such as diamonds or sapphires, which can scratch the surface of the rubellite.
- Protect from Impact: Rubellite is relatively durable, but it can still chip or crack if subjected to sharp impacts. Store your jewelry in a soft-lined case or padded box to protect it from accidental bumps or drops.
Handling
- Avoid Exposure to Chemicals: Rubellite should be kept away from household chemicals, such as bleach, ammonia, and cleaning agents, as these can damage the gemstone. Remove your rubellite jewelry before engaging in activities that involve exposure to chemicals, such as cleaning or gardening.
- Temperature Sensitivity: Rubellite is sensitive to extreme temperature changes, so avoid exposing it to sudden shifts in temperature. For example, do not leave your jewelry in a hot car or near a heat source, as this can cause thermal expansion and lead to fractures.
Professional Care
- Regular Inspections: Have your rubellite jewelry inspected by a professional jeweler at least once a year. They can check for any signs of wear, loose prongs, or damage to the gemstone. Regular inspections can help identify potential issues before they become serious problems.
- Repolishing: Over time, the surface of rubellite may develop fine scratches or lose its luster. A professional jeweler can repolish the gemstone to restore its original shine and beauty.
Conclusion
In conclusion, rubellite is a beautiful and durable gemstone with a hardness of 7 to 7.5 on the Mohs scale. While it is not as hard as some other popular gemstones, such as diamond or sapphire, its hardness is sufficient for most jewelry applications. However, proper care and maintenance are essential to ensure the longevity of your rubellite jewelry. By understanding the factors that affect rubellite’s hardness and following the appropriate care guidelines, you can enjoy the beauty and durability of this stunning gemstone for years to come.
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