Schopf T J, Allan J R
Science. 1970 Jul 17;169(3942):280-2. doi: 10.1126/science.169.3942.280.
Calcium, magnesium, and strontium occur in approximately constant ratios in traverses through skeletal walls of a single mineralogy (either calcite or aragonite). Skeletal walls of more than one mineralogy have the magnesium-rich layer (calcite) surrounding the living chamber and the strontium-rich layer (aragonite) on the outside. In contrast, phosphorus may be present in greater or lesser amounts in different parts of the same calcite skeletal wall. Aragonitic crystallites appear oriented roughly perpendicular to skeletal walls, whereas calcitic crystallites are parallel to skeletal walls.
在穿过单一矿物学（方解石或文石）的骨骼壁时，钙、镁和锶以大致恒定的比例出现。具有不止一种矿物学的骨骼壁有富含镁的层（方解石）围绕着居住腔，而外部是富含锶的层（文石）。相比之下，在同一方解石骨骼壁的不同部位，磷的含量可能或多或少。文石微晶似乎大致垂直于骨骼壁排列，而方解石微晶则与骨骼壁平行。
