Dinosaur Bone Identification Guide

How to Identify Dinosaur Bone

Finding a chunk of rock and wondering if it might be dinosaur bone is one of the most exciting moments in fossil collecting. Fossilized dinosaur bone has a distinct set of characteristics that, once you learn them, make identification fairly reliable even in the field. Here’s how to tell if that heavy, odd-looking rock is actually a piece of a creature that lived millions of years ago.

The Tongue Test

This is the single most famous field test for fossil bone, and it genuinely works.

How it works: Touch the tip of your tongue to a clean, broken surface of the specimen. If it is fossilized bone, your tongue will stick slightly --- you’ll feel a gentle suction or adhesive pull. If it’s ordinary rock, your tongue will touch it and come away cleanly.

Why it works: Fossilized bone retains the microscopic porous structure of the original bone tissue, even after mineralization. These tiny pores (the Haversian canals and other vascular channels) create capillary action that pulls moisture from your tongue, producing the characteristic “sticking” sensation.

Important caveats:

• The tongue test works best on a freshly broken or unweathered surface. Heavily weathered exterior surfaces may not stick.
• Some other porous materials (like certain sandstones or volcanic pumice) can also stick to your tongue, so this test is suggestive but not definitive.
• Make sure the rock is clean before licking it. Avoid testing specimens near contaminated areas.

Cross-Section Texture

The most diagnostic feature of dinosaur bone is its internal structure when seen in cross-section.

• Spongy or cancellous texture: The interior of most dinosaur bone shows an irregular, spongy network of mineralized bone tissue. This looks distinctly organic --- like a hard sponge turned to stone.
• Haversian canals: Under magnification (a 10x hand lens is sufficient), you can often see tiny circular or oval channels running through the bone. These are the fossilized remnants of blood vessel channels in the living bone.
• Cortical (compact) bone: The outer layer of limb bones is denser and smoother than the spongy interior. If you find a piece with a dense outer rind grading into spongy interior, that is a very strong indicator of bone.
• No growth rings or parallel fibers. This is what separates bone from petrified wood. Wood shows concentric growth rings and parallel grain; bone shows an irregular meshwork.

Weight and Density

Dinosaur bone that has been fully permineralized (the original bone minerals replaced or infused with silica, calcite, or iron minerals) is noticeably heavy for its size. Pick up a piece of fossil bone and a piece of ordinary sandstone of the same size --- the bone will almost always feel heavier.

This is because the pore spaces in the original bone were filled with dense minerals during fossilization. Common replacement minerals include:

• Agate/chalcedony (silica) --- produces bone that is very hard and often colorful
• Calcite --- common in many formations, produces moderately heavy bone
• Iron minerals (hematite, goethite) --- produces very heavy, dark-colored bone
• Pyrite --- occasionally fills bone, making it extremely heavy with a metallic sheen

Color

Dinosaur bone comes in a wide range of colors depending on the mineralogy of replacement:

• Brown to tan --- the most common color, typical of calcite or mixed-mineral replacement
• Black --- often indicates manganese or organic carbon preservation
• Red, orange, rust --- iron oxide replacement (hematite, limonite)
• Blue, red, yellow banded --- agate-replaced bone (gem bone), especially common in the Morrison Formation of Utah and Colorado
• Cream to white --- sometimes seen in chalk or limestone-hosted specimens

Color alone is never diagnostic. Always combine color observations with texture and the tongue test.

How to Distinguish Dinosaur Bone from Common Look-Alikes

Dinosaur Bone vs. Petrified Wood

This is the most common confusion. Key differences:

• Wood has parallel grain lines and concentric growth rings. Bone has an irregular spongy meshwork.
• Wood often shows a fibrous texture on broken surfaces. Bone shows rounded pore spaces.
• Both can stick to your tongue if porous, but the internal structure under a hand lens will resolve the question.

Dinosaur Bone vs. Ironstone Concretions

• Concretions form around a nucleus in sedimentary rock and are typically uniform inside --- no pore structure, no cell channels.
• Bone shows biological texture. Break open a concretion and you’ll see homogeneous or radial mineral patterns, not spongy bone.
• Concretions are often spherical or oval; bone fragments are irregular.

Dinosaur Bone vs. Volcanic Rock (Vesicular Basalt)

• Vesicular basalt has gas bubble holes (vesicles) that can superficially resemble the porous texture of bone.
• Key difference: basalt vesicles are round and randomly distributed. Bone pores are irregular and follow biological patterns (channels, mesh networks).
• Basalt is typically dark gray to black and very hard. It will not stick to your tongue.
• Basalt is an igneous rock and will never be found in sedimentary dinosaur-bearing formations if you’re paying attention to your geology.

Common Dinosaur Bone Types Found by Amateurs

Most amateur finds are not complete skeletons or even complete bones. The vast majority of dinosaur bone discovered by non-professionals falls into these categories:

Limb Bone Fragments

Pieces of femora (thighbones), tibiae (shinbones), humeri (upper arm bones), and other long bones are among the most commonly found fragments. They’re recognizable by their dense outer cortical bone surrounding a spongy interior. Even small fragments can be identified by this two-layer structure.

Rib Fragments

Dinosaur ribs are long, curved, and relatively thin. Rib fragments are common surface finds because ribs break easily during weathering. They show a thin cortical layer and minimal spongy interior.

Vertebra Fragments

Pieces of vertebrae are commonly found, especially the boxy central body (centrum) of the vertebra. Centra often have a distinctive concave surface on one or both ends and dense spongy bone throughout.

Tendon Bone

Many dinosaurs, especially hadrosaurs and some theropods, had ossified (bony) tendons along their spines. These appear as rod-shaped or flat bone fragments and are extremely common in formations like the Hell Creek.

Unidentifiable Fragments

Honestly, most dinosaur bone found on the surface consists of small, weathered fragments that cannot be assigned to a specific skeletal element. That’s perfectly normal. A fragment of genuine dinosaur bone is still a remarkable find regardless of whether you can tell exactly which bone it came from.

What to Do If You Find Dinosaur Bone

1. Note the exact location using GPS coordinates or a detailed description.
2. Photograph it in place before picking it up, with a scale object (coin, pen) for size reference.
3. Check your land status. If you’re on federal land, do not collect it --- vertebrate fossils are protected. Mark the location and report it to the local BLM or Forest Service office.
4. On private land with permission, you may collect it. Handle it gently; fossil bone can be fragile.
5. If it appears to be part of a larger specimen (you see more bone emerging from the rock), stop digging. You may be looking at a partial skeleton, and improper excavation can destroy scientific data. Contact a local museum or university paleontology department.

The thrill of holding a piece of bone from an animal that lived tens or hundreds of millions of years ago never gets old. Learn these identification techniques, practice them in the field, and you’ll develop an eye for bone that serves you for a lifetime of collecting.

Commonly Confused With

• Petrified wood
• Ironstone concretions
• Volcanic rock

Where to Find Them