Ivory is a dense, hard material derived from the tusks and teeth of certain animals, primarily elephants. Composed mainly of dentine, it has been valued for centuries due to its distinct appearance and perceived robustness. Historically, it was associated with luxury and durability across various cultures. The public generally regards ivory as a strong material, a perception rooted in its widespread use in items requiring resilience and intricate detail.
Understanding Ivory’s Mechanical Properties
Ivory’s strength stems from its mechanical properties and biological composition. It is a biomineral composite, primarily consisting of dentine—a blend of fibrous protein collagen and a mineral component, largely calcium phosphate. This layered structure contributes significantly to its durability.
Ivory’s hardness resists scratching and abrasion. On the Mohs scale, elephant ivory typically ranges from 2 to 3. This places it in a moderately hard category, allowing it to maintain its form and surface integrity. Its density, a contributing factor to its robustness, generally falls between 1.70 and 1.93 grams per cubic centimeter (g/cm³). This compactness indicates a tightly packed internal structure.
Ivory also exhibits considerable elasticity, meaning it possesses flexibility before fracturing. This property, combined with its tenacity—resistance to breaking or tearing—enables ivory objects to withstand impacts and stresses without immediately shattering. While specific quantitative values for compressive and tensile strength are less commonly detailed, its historical applications attest to its capacity to endure significant mechanical forces.
Variables Affecting Ivory’s Strength
Ivory’s inherent strength and characteristics vary based on biological and environmental factors. The animal source plays a significant role; while elephant ivory is widely known, ivory from mammoths, walruses, and hippopotamuses possesses distinct properties. Mammoth ivory, for example, is often noted for being harder, sometimes registering 3 to 5 on the Mohs scale.
The animal’s age and the specific part of the tusk or tooth also influence ivory’s properties. Tusks grow in layers, and the internal structure can change from a hollow cavity near the skull to a solid material towards the tip. This variation in density and structure within a single tusk can affect its strength.
Environmental conditions after harvesting, such as moisture and temperature, also impact ivory’s long-term stability. As an organic material, ivory contains water, and significant changes in humidity can lead to dehydration. This can cause cracks, particularly along its natural growth lines, affecting its structural integrity and aesthetic over time.
Historical Uses and Material Durability
Ivory’s unique combination of properties made it a highly sought-after material for numerous historical applications. Its fine grain and ability to hold intricate detail made it ideal for elaborate carvings, such as figurines and decorative inlays. These artistic applications showcase ivory’s workability and its capacity to maintain complex forms over long periods.
Beyond ornamental uses, ivory’s durability and smooth finish led to its selection for functional items like piano keys and billiard balls. Its resilience ensured these items could withstand repeated impact and handling without significant wear or degradation. Ivory’s ability to resist chipping and its smooth texture were advantageous for billiard balls, providing consistent play.
Ivory was also utilized for cutlery handles and game pieces, demonstrating its capacity to endure frequent use and maintain its integrity. Its organic nature meant it was less prone to corrosion compared to some metals, and it offered greater stability than wood in certain applications. Many antique ivory objects have survived for centuries, attesting to the material’s long-term durability and its resistance to decay when preserved under stable conditions.
Ivory’s Strength in Comparison
Comparing ivory to common materials provides valuable context for its strength. Ivory’s density, typically around 1.70-1.93 g/cm³, is lower than aluminum (approximately 2.7 g/cm³) but higher than common plastics like acrylic (about 1.15-1.19 g/cm³). Human bone, particularly compact bone, can have a density ranging from 1.9 to 2.1 g/cm³, making it somewhat comparable to ivory. Oak wood, a common hardwood, is significantly less dense, around 0.7 g/cm³.
In terms of hardness, ivory’s Mohs scale rating of 2 to 3 means it is harder than some plastics like polyethylene (Mohs 2) and acrylic (Mohs 2.5), but generally softer than polycarbonate (Mohs 3). Aluminum, depending on its alloy, typically has a Mohs hardness of 2.5 to 3.
Considering elasticity, ivory is a resilient material. Human bone exhibits a wide range of elastic moduli (cortical bone typically 15-26 GPa), and oak wood’s elastic modulus ranges from 10 to 14 GPa. Acrylic plastics generally have a lower elastic modulus (often 2.8-3.3 GPa), while aluminum is considerably stiffer (around 70 GPa). These comparisons illustrate that ivory offers a unique balance of properties, being dense and moderately hard, with an elasticity that allowed for its diverse historical applications.