A ruby is a naturally occurring, precious gemstone defined as the red variety of the mineral corundum, which is chemically composed of aluminum oxide (Al₂O₃). The vibrant red color is caused by trace amounts of chromium incorporated into the crystal structure. This composition grants rubies a reputation for being exceptionally durable, leading to a common belief that these stones are practically indestructible. Determining if a focused, blunt impact can shatter a ruby requires understanding its specific physical properties.
Hardness: What Rubies Resist
Mineralogists define hardness as a material’s resistance to scratching and abrasion, a property measured using the Mohs scale of mineral hardness. On this scale, which ranges from 1 to 10, ruby and its sister stone, sapphire, achieve a rating of 9. This places corundum as the second hardest natural mineral, surpassed only by diamond, which rates a 10.
The high Mohs rating means a ruby cannot be scratched by common materials like quartz, glass, or most metals. This exceptional scratch resistance is why the stone is highly valued in jewelry, particularly for pieces subject to daily wear, such as rings. A ruby’s surface will generally remain pristine even when constantly exposed to dust, which often contains abrasive silica particles.
Toughness and Cleavage: What Rubies Do Not Resist
While hardness measures resistance to scratching, toughness measures a material’s resistance to breaking, chipping, or fracturing under impact. Despite its high hardness, a ruby is considered brittle. This brittleness is the structural weakness that can lead to catastrophic failure when the stone is struck.
Corundum crystals also exhibit a structural feature known as parting, which is a plane of weakness that acts similarly to cleavage in other minerals. This parting occurs because of the crystal’s atomic structure and can be exploited when a sudden, concentrated force is applied. If a ruby is hit along one of these planes, the material may fracture cleanly. The presence of internal flaws, such as microscopic cracks or mineral inclusions, further reduces the stone’s overall toughness.
The Answer: Applying Force to a Ruby
The answer to whether a hammer can break a ruby is definitively yes, because the concentrated, sudden energy of a hammer blow exploits the stone’s brittleness and parting planes. A hammer delivers kinetic energy too rapidly for the ruby’s crystal lattice to absorb or dissipate without fracturing. The force overcomes the relatively weak bonds along the internal structural planes.
The outcome of the impact depends heavily on the stone’s condition and the point of impact. Rubies containing natural inclusions, often called “silk,” or those that have undergone certain heat or fracture-filling treatments are substantially more vulnerable. Fracture-filled rubies, for instance, have internal cracks filled with glass, which is far weaker than the corundum itself and can shatter easily upon impact.
Striking the ruby on a delicate edge or a natural parting plane will cause the stone to chip or split much more easily than hitting a broad, flat surface. The hammer blow is a test of toughness, a test the ruby is scientifically structured to fail.