Agatized dinosaur bone, sometimes referred to as “gembone” or “dinogem,” represents a rare and visually striking form of fossilization. Unlike typical fossilized bone, this material exhibits a colorful, glassy appearance, making it highly sought after by collectors and enthusiasts alike. Its unique beauty stems from a complex geological process that replaces the original bone with durable, vibrant minerals.
The Agatization Process
Agatized dinosaur bone forms through a process called permineralization, where original organic material is replaced by minerals. After a dinosaur’s death, its bones must be buried quickly, often by sediment or volcanic ash, to protect them from decay. Over extended periods, groundwater rich in dissolved silica, the primary component of agate and chalcedony, seeps into the porous bone structure. This silica-rich solution fills the microscopic voids within the bone.
The original bone material, primarily calcium phosphate, dissolves and is systematically replaced by crystallizing silica. This mineral substitution results in a remarkably faithful preservation of the bone’s internal architecture. The newly formed silica minerals, typically microcrystalline quartz, impart exceptional hardness and a waxy to glassy luster to the fossil.
Distinctive Visual Markers
Identifying agatized dinosaur bone relies on recognizing its unique visual characteristics, especially preserved internal structures. A primary indicator is the presence of cellular patterns, often visible on polished or fractured surfaces. These patterns can appear as intricate webbing, a spongy texture resembling bone trabeculae, or distinct Haversian canals that once housed blood vessels.
The coloration of agatized dinosaur bone is another distinguishing feature, ranging broadly from common browns and grays to vibrant reds, yellows, oranges, blues, and greens. These diverse hues result from various mineral impurities, such as iron oxides for reds and yellows, or manganese dioxide for purples and blacks, incorporated during the agatization process. The material can be translucent, particularly along thinner edges, allowing light to pass through it.
Agate banding, characterized by concentric layers or swirling patterns, can sometimes be observed within the fossil. The overall shape of the specimen typically retains the general form of a bone fragment, such as curved or tubular sections, or remnants of a marrow cavity. This combination of internal patterns, varied color, translucence, and original bone morphology helps differentiate agatized dinosaur bone from other geological materials.
Common Lookalikes and How to Differentiate
Several other natural materials can be confused with agatized dinosaur bone. Petrified wood, though also formed by silica replacement, displays distinct wood grain patterns like tree rings and wood fibers, rather than bone cellular structures. This helps distinguish it from the intricate, organic patterns found in agatized bone.
Other forms of agate or chalcedony, such as plain nodules or geodes, may exhibit similar colors and translucence but lack any preserved organic structure or bone-like shape. Chert and flint, also microcrystalline quartz, are typically opaque and do not possess the distinctive cellular patterns or translucence seen in agatized bone.
Some weathered igneous rocks might share similar colors, but they typically lack the specific internal patterns and glassy or waxy texture. Their crystalline structure, if visible, will not resemble biological cellular arrangements. Examining the specimen for the unique combination of cellular preservation, translucence, and luster is key to avoiding misidentification.
Simple Field Tests for Confirmation
Several simple, non-destructive field tests can assist in identifying agatized dinosaur bone. Its hardness, typically 6 to 7 on the Mohs scale, means it can scratch glass or steel, a straightforward test with a knife blade or glass bottle.
Holding the specimen up to a light source can reveal its characteristic translucence, especially noticeable along thinner edges where light might pass through. Using a magnifying glass or a jeweler’s loupe helps examine the surface for microscopic cellular structures, such as Haversian canals or osteon remnants, which are definitive indicators of fossilized bone.
Gently tapping the specimen may produce a clear, ringing sound, contrasting with the dull thud often heard from less dense or non-mineralized materials. While the “lick test” is sometimes mentioned for porous, non-agatized bone, it is not reliable for agatized dinosaur bone due to its dense, non-porous nature.