Thermogravimetric analysis linked to mass spectrometry (TGA-MS) shows changes in mass and identifies gases evolved when a material is heated. Heating to 600°C enabled samples of bone to be classified as having a high (cod clythrum, deer antler, and whale periotic fin bone) or a low (porpoise ear bone, whale tympanic bulla, and whale ear bone) proportion of organic material. At higher temperatures, the mineral phase of the bone decomposed. High temperature X-ray diffraction (HTXRD) showed that the main solids produced by decomposition of mineral (in air or argon at 800°C to 1000°C) were
$
{\text{Ca}}_{{\text{10}} - {\text{x}}} {\text{V}}^{{\text{(Ca)}}} _{\text{x}} [({\text{PO}}_{\text{4}} )_{{\text{6}} - {\text{x}} - {\text{y}}} ({\text{HPO}}_{\text{4}} )_{\text{x}} ({\text{CO}}_{\text{3}} )_{\text{y}} ][({\text{OH}})_{{\text{2}} - {\text{x}} - {\text{y}}} ({\text{CO}}_{\text{3}} )_{\text{y}} {\text{V}}^{{\text{(OH)}}} _{\text{x}} ]
$
{\text{Ca}}_{{\text{10}} - {\text{x}}} {\text{V}}^{{\text{(Ca)}}} _{\text{x}} [({\text{PO}}_{\text{4}} )_{{\text{6}} - {\text{x}} - {\text{y}}} ({\text{HPO}}_{\text{4}} )_{\text{x}} ({\text{CO}}_{\text{3}} )_{\text{y}} ][({\text{OH}})_{{\text{2}} - {\text{x}} - {\text{y}}} ({\text{CO}}_{\text{3}} )_{\text{y}} {\text{V}}^{{\text{(OH)}}} _{\text{x}} ]
where V
(Ca) and V
(OH) correspond to vacancies on the calcium and hydroxide sites, respectively, and 2–x–y = 0.4. This general formula is consistent in describing both mature bone mineral (i.e., whale bone), with a high Ca/P molar ratio, lower HPO
42– content, and higher CO
32– content, and immature bone mineral (i.e., deer antler), with a low Ca/P ratio, higher HPO
42–, and lower CO
32– content.