Agatized dinosaur bone, often called gembone, is a rare geological material formed when the original organic bone is entirely replaced by a stable, crystalline mineral structure. This unique process creates a collectible material of exceptional beauty and durability, combining biological patterns with mineral properties. Correct identification requires understanding the specific geological process and knowing which physical characteristics to look for. Because of its scarcity and value, learning to distinguish gembone from common stone is necessary for collectors and enthusiasts.
Understanding Agatization
Agatization is a specific form of permineralization where the replacement mineral is silica, typically agate or chalcedony. The process begins when the bone is rapidly buried in an oxygen-excluding environment, slowing decay. Over millions of years, groundwater saturated with dissolved silicon dioxide permeates the porous bone structure. This silica-rich solution fills voids within the bone, including marrow cavities and vascular channels.
The original bone material, primarily calcium phosphate, gradually dissolves and is concurrently replaced by the precipitating silica. This cell-by-cell substitution preserves the bone’s microscopic architecture with remarkable fidelity. As the silica solidifies, it forms microcrystalline quartz, resulting in the hard, glassy material known as agatized bone. The vibrant colors often seen in gembone are caused by trace elements in the groundwater, such as iron oxides for reds and yellows, or manganese for blues and purples.
Recognizing Cellular Structure and Patterns
The most definitive way to identify agatized dinosaur bone is by observing the preserved biological structure. When a specimen is cut and polished, the internal cross-section reveals a pattern often described as “spider-webbing.” This pattern is the fossilized remnant of the bone’s trabecular structure, the spongy matrix that once surrounded the marrow.
Within this structure, one can see the circular outlines of the Haversian canals, which were channels for blood vessels and nerves. The bone’s cross-section is not uniform; the dense cortical bone, or exterior layer, appears solid and uniform in color. This dense exterior contrasts sharply with the cancellous bone of the interior, which displays the porous, web-like pattern of the marrow cavity. The silica replacement gives the material a glassy luster when polished, and thin slices may exhibit translucency.
Practical Physical Tests for Verification
Because agatized dinosaur bone is essentially microcrystalline quartz, its mineral composition allows for simple, non-destructive tests to confirm its identity. The primary physical property to confirm is the hardness of the material. Agate and chalcedony register approximately 7 on the Mohs scale of mineral hardness, which is harder than common glass.
A practical test involves attempting to scratch the specimen with a common steel file or a piece of quartz. If the material is authentic, the steel should not leave a scratch, but the specimen may scratch the steel or glass. High density is another verification method, as the bone’s porous structure has been filled with dense mineral matter. An authentic specimen will feel noticeably heavier than a similarly sized piece of non-agatized fossil.
Common Materials Mistaken for Agatized Dinosaur Bone
Several materials can be confused with agatized dinosaur bone. Petrified wood is one common look-alike, as it is also a silica-replaced fossil, but examination reveals the linear, concentric rings of wood grain instead of the web-like structure of bone. Non-agatized fossil bone is another frequent point of confusion, but this material is typically softer, features a duller, stony texture, and lacks the vibrant colors and glassy luster of silica replacement.
Banded agate can sometimes be mistaken for gembone due to similar coloring and hardness. However, banded agate lacks the preserved biological architecture; it displays only geological banding patterns without Haversian canals or the spongy marrow structure. By focusing on the unique, preserved cellular architecture, one can confidently distinguish genuine agatized dinosaur bone from these common alternatives.