Types Of Spherules Research Articles

Electron microprobe analysis and ore microscopic study of magnetic spherules and grains collected from the Greenland ice

Numerous magnetic spherules and grains collected from the Greenland ice and suspected of being of cosmic origin were studied microscopically and with the microprobe. Seven types of spherules and grams were recognized.

Black, magnetic spherules from Pleistocene and recent beach sands

Magnetic spherules have been discovered in the natural concentrates of ilmenite and other heavy minerals that occur in beach sands of both Pleistocene and recent age. The spherules range in size from 80 to 650 μ. Those in any given deposit match the grain size of the matrix sand. The spherules consist mainly of magnetite (FeFe 2O 4), hematite (α-Fe 2O 3) and wüstite (Fe 1− x O). No metal-bearing ones have been found to date. Electron-microscope analyses show that our samples contain three distinct chemical types of spherules: Type I is approximately 70% iron, 5% nickel, 0.3% cobalt and 0.2% chromium. Type II consists solely of 70% iron (oxygen is estimated at 30 %) or of 70 % iron plus 0.5 % manganese. Type III are iron-poor, glassy spherules that are rich in SiO 2, Al 2O 3 and minor elements. Type I spherules occur in a Pleistocene sand in Florida and in a recent one in Brazil. Although they are nonmetallic, they contain nickel and cobalt in meteoritic proportions and we believe they are of extraterrestrial origin. Type II spherules occur in both Pleistocene and recent sands, in the Greenland ice cap, and in samples from many other environments. Their origin remains unknown. Type III spherules were found only in a modern beach, where industrial contamination is likely and in a sample of sand processed in a dry mill. Spherules of this type may be either volcanic or industrial.

Determination of the densities of individual meteoritic, glacial, and volcanic spherules

We have determined the individual densities of 72 small (diameters between 15 and 100 μ) spherules of three distinct types: (1) found in polar ice, (2) collected near known volcanoes, and (3) produced in the laboratory from meteoritic samples. The average densities of these three types of spherules are 4.54, 2.75, and 4.92 g/cm³, respectively, lending support to the claim that most polar spherules do not have a volcanic origin.