Labradorite is a captivating feldspar mineral cherished primarily for its distinctive optical phenomenon known as labradorescence. This effect causes a brilliant, directional flash of iridescent colors, typically blues, greens, and golds, that appears to shift across the stone’s surface as it is moved. As a member of the plagioclase feldspar group, understanding its inherent physical properties is important for its use in jewelry and decorative objects. Assessing a mineral’s durability, particularly its resistance to surface damage and breaking, determines how the material can be safely handled and worn.
Scratch Resistance on the Mohs Scale
The resistance of labradorite to scratching is measured using the Mohs scale of mineral hardness, a qualitative scale ranging from 1 (softest) to 10 (hardest). Labradorite typically registers a hardness rating between 6 and 6.5 on this scale. This placement means the mineral is moderately resistant to abrasion, but it is not impervious to damage.
Materials with a lower Mohs rating, such as a copper penny (3.5) or a steel knife blade (5.5), are softer and would not scratch labradorite. However, this hardness rating is just below that of common quartz, which is a 7 on the scale. Since quartz is a major component of common dust and sand, labradorite is susceptible to scratching from airborne particles or grit. Storing or wearing labradorite alongside materials rated 7 or higher, such as topaz (8) or diamond (10), will almost certainly result in surface damage.
Understanding Cleavage Planes
While the Mohs scale measures a mineral’s scratch resistance, it does not account for its tenacity, which is its resistance to breaking or chipping from impact. Labradorite, like all feldspar minerals, possesses a structural vulnerability known as cleavage. Cleavage refers to a mineral’s tendency to break smoothly along specific planes of weakness within its crystal lattice.
Labradorite exhibits two distinct, perfect cleavage planes that intersect at an angle very close to 90 degrees. These planes represent surfaces where the atomic bonds are weaker, allowing the stone to split cleanly when struck with sufficient force. Due to this internal structure, a sharp blow or impact, especially on the edge of a cut gemstone, can easily cause the stone to chip or split along these planes. This susceptibility to impact damage is a separate consideration from its moderate Mohs hardness.
The presence of these perfect cleavage planes means that even though labradorite is reasonably hard against scratching, it is structurally fragile. This characteristic is particularly important in jewelry, as stones set in rings or bracelets are more likely to encounter accidental impact than those set in pendants or earrings. Therefore, the internal structure of the crystal dictates that a labradorite gemstone requires careful setting and wear to avoid breaking.
Handling and Care Guidelines
Due to the combination of moderate hardness and structural cleavage, proper handling of labradorite is necessary to maintain its appearance. When cleaning the stone, use only warm water and a mild, non-detergent soap. A soft cloth should be used for gentle scrubbing to avoid introducing scratches from any potential abrasive particles.
Avoid mechanical cleaning methods, such as ultrasonic cleaners or steam cleaners, because the vibrations and heat can exacerbate internal flaws and cause the stone to fracture along its cleavage planes. Keep the mineral away from harsh household chemicals, including bleach, ammonia, and strong acids, which can potentially dull the stone’s finish. Always store labradorite jewelry separately from harder gemstones like sapphires or diamonds to prevent surface abrasion.