Studies on the Various Kinds of the Limestones in the Ryukyu Islands

The various limestones in the Ryukyu Islands were classified according to the formation circumstances of limestones into four groups, which are hard limestone, soft limestone, crystallized limestone, and coral. The physical and chemical characters of the various kinds of the limestone in the Ryukyu Islands were studied for the purpose of clarifying the original nature of a limestone. The major and minor components of the limestones, such as calcium, magnesium, iron, aluminum, silica, phosphorus, manganese, sulfate, chlorine, and sodium, were analyzed, and also the specific gravity and particle size of the limestones were measured. The following results were obtained: 1. The contents of silica, iron, aluminum, and phosphorus in the various limestones decrease in the followillg sequence:hard limestone, soft limestone, crystallized limestone, coral. 2. There is a positive correlation between the amounts of iron+aluminum and silica in the three kinds of the limestones. The facts shown above suggest that these limestones contain much more iron aluminum silicate impurities than the coral does. 3. The difference of the magnesium contents between hard limestone and soft limestone can not be distinguished, Nevertheless, hard limestone contains more amounts of magnesium than crystallized limestone does. 4. The manganese contents of the limestones decrease in the following sequence:Hard limestone, crystallized limestone, coral. There is no difference of the manganese contents between hard limestone and soft limestone. There is a positive relationship between the amounts of manganese and iron+aluminum in the limestones. 5. The sulfate contents of the limestones decrease in the following sequence: coral, soft limeston hard limeston crystallized limestone. The sulfate contents of the coral is O.57% on the average. 6. The chlorine contents of the various limestones vary from 0.0022 to 0.037% and decrease in the following sequence:coral, soft limestone, hard limestone, crystallized limestone. 7. The sodium contents of the limestones vary from 0.005 to 0.33% and decrease in the following sequence:coral, soft limestone, hard limestone crystallized limestone There is a positive relationship between the contents of sodium and chlorine in the limestones. There is no positive correlation between the amounts of chlorine and sulfate in the limestones. The facts shown above suggest that the chlorine enter as sodium chloride in the limestones. 8. The specific gravity of the various limestones vary from 2.35 to 2.80 and decrease in the following sequence: coral, crystallized limestone, hard limestone, soft limestone. 9. The results of X-ray diffraction methods indicate that the three kinds of the limestones consist of calcite structure, and the coral consists of aragonite or calcite structures