ART. 16 CAVE PEARLS FEOM NEW MEXICO HESS S 



and chlorine. A specimen of phosphate rock from Idaho is shown 

 in Plate 4. KSome deposits of iron carbonate have perhaps been laid 

 down in the same way and later recrystallized, so that their oolitic 

 structure is indistinct. The great beds of oolitic iron ores probably 

 have been precipitated in a similar manner. In at least three small 

 crater lakes of Japan, where the water is agitated by sulphurous 

 gases, oolites of sulphur are formed, and in one of them in great 

 enough quantity to be profitably exploited.^ 



Nor is the formation of oolites confined to solutions in liquids. Pre- 

 cipitation of a substance from any moving fluid, such as air or other 

 gases, may produce solids of the same type. In the Mond process of 

 obtaining nickel from its ores the nickel is converted to nickel car- 

 bonyl, a gas, and advantage is taken of the principle that substances 

 precipitating in an agitated fluid may be collected as oolites. The 

 gas is run into a reductor and heated somewhat above its decomposi- 

 tion point. Fine granules of nickel are rolled through the decom- 

 posing gas and as the nickel separates from the gas it collects on the 

 granules, and ' thus, metallic balls, true nickel oolites, are formed. 

 (See pi. 5.) Thousands of tons of nickel are annually obtained by 

 this process. 



Hailstones are probably formed according to the same principle. 

 A number of snowflakes are matted together by swirling air, or a 

 group of other ice molecules are collected together, and on the mass as 

 a nucleus ice is deposited directly from gaseous water in an atmos- 

 phere below the freezing point, making concentric shells very similar 

 in their structure to calcite oolites till hail finally falls as the familiar 

 enemy of crops and greenhouses. Cross sections of large hailstones 

 are very similar to the cross sections of oolites from Carlsbad Cav- 

 erns, shown in Plates 6 and 7.^ Oolites of calcite are formed in boil- 

 ing sugar refinery refuse in the process of making by-product alcohol. 

 They are formed rapidly and are fairly large, I14 inches or more in 

 longest diameter. Those seen are of coarse texture and do not have 

 smooth surfaces. 



The dense and the more visibly crystalline layers or shells in the 

 oolites from Carlsbad Caverns have evidently formed under different 

 conditions and the dense polished layers are probably formed by slow, 

 steady accretion. 



Some of the oolites from Carlsbad Caverns are elongated or other- 

 wise vary from a spherical form. (See pis. 7 and 8.) Their form 

 is largely determined by that of the nucleus. An elongated oolite, 

 shown in polished section in Plate 5, Figure 1, tells its own story. 



2 Oinouye, Y., A peculiar process of sulphur deposition, Journal of Geology, vol. 24, 1916, 

 pp. 806-808. 



» A good illustration of hailstones showing concentric structure and radial crystallization 

 is given in " Lehrbuch der Meteorologie," by Jul. von Hann, Leipzig, 1915, pi. 25, opposite 

 page 708. 



