Final answer:
During fossilization, bone is often partially replaced by silica, iron, or calcite, leading to the preservation of the bone's structure with new mineral composition.
Step-by-step explanation:
When bone is mineralized during fossilization, it is partly replaced by silica, iron, or calcite. This process of replacement is known as the substitution of original skeletal material by a secondary mineral. For instance, silica can replace the calcite of an oyster shell on a molecule-by-molecule basis, and the fossiled remains may retain fine cellular detail even though the composition has changed. The most common minerals involved in the replacement during fossilization are silica (quartz), pyrite, dolomite, and hematite. The spectacular fossils created through pyrite replacement, especially those found in black shales, underscore the varying nature of fossilization processes.