sedimentary

Dinosaur Bone (Gembone)

Petrified Dinosaur Bone (Apatite/Silica replacement)

Hardness: 6.5–7 on Mohs scale; Color: Dark brown, tan, and black with visible cellular web-like patterns; Luster: Vitreous to waxy (when polished); Structure: Cryptocrystalline replacement of spongy bone tissue; Specific Gravity: 2.6–2.7.

Hardness: 6
Luster: Vitreous to waxy (when polished)

Identified March 14, 2026More sedimentary →

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Physical properties

Formation & geological history

Formed through permineralization where minerals (usually silica) leach into the porous spaces of bone. Most gembone in the USA dates to the Jurassic period (approx. 150 million years ago), specifically from the Morrison Formation.

Uses & applications

Primarily used in high-end lapidary work, jewelry (cabochons), and as scientific or investment specimens for fossil collectors.

Geological facts

Gembone is considered one of the rarest fossil materials in the world because it requires specific geological conditions to agatize cells without crushing the bone. Famous specimens often retain the original biological 'marrow' structure in vibrant colors.

Field identification & locations

Identify by looking for the 'honeycomb' or 'cell' pattern characteristic of trabecular (spongy) bone. In the field, look for weathered, petrified fragments with a porous texture in known fossil-bearing strata like those in Utah, Colorado, and Wyoming.

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