A ruby is a red variety of the mineral corundum, which is second only to diamond in hardness. Its extreme durability often leads to the mistaken belief that the stone is indestructible. While highly resistant to daily wear, a ruby is not impervious to all forms of stress. Understanding how a ruby can be harmed is the first step in ensuring its longevity.
Ruby’s Resistance to Scratching (Mohs Hardness)
A ruby’s reputation for strength comes from its superior surface hardness, measured on the Mohs scale of mineral hardness. This qualitative scale, ranging from 1 (talc) to 10 (diamond), determines a material’s resistance to scratching. Ruby, along with sapphire, ranks at a 9, establishing it as an exceptionally hard material.
This high ranking means that almost all common materials cannot scratch a ruby’s polished surface. Dust often contains quartz (Mohs 7), which is an abrasive threat to softer gems. A ruby’s superior hardness protects it from this environmental scratching, helping it retain its bright polish. This resistance makes the ruby an excellent choice for jewelry intended for everyday use.
Brittleness and Parting: The Vulnerability to Breaking
It is crucial to distinguish between a gem’s hardness (scratch resistance) and its tenacity (resistance to impact and shattering). Most gemstones, including ruby, are brittle, meaning they can shatter even though they are very hard.
Corundum, the mineral group to which ruby belongs, does not have a true cleavage, which is a tendency to break along planes of atomic weakness. However, it possesses a characteristic called parting, a similar structural weakness occurring along specific planes due to twinning or stress. A sharp, hard impact delivered at the right angle can exploit these parting planes, causing the ruby to fracture, chip, or break completely.
Common Causes of Ruby Damage
The most direct way a ruby can be broken is through a high-force impact that exploits its inherent brittleness. A severe knock against a hard surface can generate enough force to cause a fracture, especially if the blow is concentrated on a thin edge or a vulnerable spot in the setting. This physical trauma can lead to chips along the girdle or pavilion, or even a complete break if the impact hits a parting plane.
Another significant threat is thermal shock, which involves a sudden, extreme change in temperature. Corundum is sensitive to these rapid shifts; exposing a ruby to intense heat followed quickly by cold can cause internal stresses. For example, dropping a hot stone into cold water can cause the stone to fracture or crack internally.
Rubies with internal imperfections, known as inclusions, are also far more susceptible to damage. These natural features, such as internal fractures or tiny trapped crystals, represent pre-existing structural weaknesses. If a ruby with significant inclusions is subjected to a strong impact or rapid temperature change, the stress will often concentrate at these flaw points, making the stone much more prone to breaking than a clean, flawless gem.
Protecting Your Ruby Gemstone
Protecting a ruby starts with mindful wear, specifically avoiding situations where the jewelry may sustain a hard blow. It is advisable to remove ruby rings and bracelets before engaging in strenuous activities, gardening, or cleaning, which present a high risk of accidental impact. Secure storage is also recommended, keeping the ruby separate from other pieces, particularly other hard gemstones.
Cleaning a ruby requires caution to prevent thermal shock damage. While untreated rubies are stable, those that have undergone certain treatments can be more vulnerable to heat. The safest method for cleaning is warm, soapy water and a soft brush, avoiding steam cleaners or sudden temperature shifts. Regular inspection by a professional jeweler can ensure that the setting prongs remain secure and are not placing undue stress on the stone.