The physical structure and appearance of the bone that makes up the Starchild Skull is radically different from normal human bone.

The bone of the Starchild Skull:

• Is about half as thick as comparable human bone,

• Weighs about half as much as comparable human bone,

• Is significantly harder to cut than human bone,

• Contains a reddish residue and microscopic fibers unlike anything seen before in human bone,

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Slight thinning of the bone does occur naturally after death, however the image below shows the Starchild Skull, which is 900 years old, compared to a 900 year old normal human skull found in the same mine tunnel, so it is a true "apples to apples" comparison. All of the Starchild Skull bone is a minimum of 50% thinner than the human bone. Various aliments such as Hydrocephaly and Osteoporosis can cause bone to become thinner, however these conditions cause the bone to become more brittle or weaker.