OOLITES OR CAVE PEARLS IN THE CARLSBAD CAVERNS 



By Frank L, Hess^ 



Custodian of Rare Metals and Rare Earths, United States National Museitm 



In 1925 Dr. Willis T. Lee, of the United States Geological Survey, 

 collected a considerable number of oolites from Carlsbad, N. Mex. 

 They included little round balls of considerable range in size, to 

 which he gave the somewhat fanciful name of " cave pearls." 

 They were found in small, round, shallow pools, and some resembled 

 eggs in a bird's nest (figs. 1 and 2, pi. 1) ; others looked like a quan- 

 tity of stone shot. Still others of the oolites were irregular in shape, 

 and were as much as 2 inches (50 mm.) long, and less thick. So 

 far as known to me, this is the first time that oolites have been found 

 in a cave, though they are common in other places. Excellent exam- 

 ples are on exhibition in the United States National Museum, and 

 their study throws an excellent light on the formation of oolites in 

 general. 



By " oolite " is ordinarily meant a tiny, more or less rounded con- 

 cretion formed of concentric layers of mineral matter. When these 

 are massed together they resemble fish roe — ^hence the name " oolite," 

 from the Greek oon^ meaning egg. 



The oolites collected by Mr. Lee range in diameter from one- 

 sixteenth of an inch (1.5 mm.) to a little more than an inch (25 

 to 30 mm.). Most of them are round, some are oval, and some ir- 

 regular in shape. Their surfaces vary as much as their forms. 

 Some are beautifully polished and opaque, and others, particularly 

 the smaller, are smooth and translucent, resembling little balls of 

 artificially polished onyx. (See pi. 1, fig. 1.) Some have the tex- 

 ture of bisque, others are much rougher. Though most are white, 

 others have a slight yellowish tint or may be clouded with yellow. 



1 Since this article was written I have found a description of irregular, smaller oolites 

 which were discovered in a Swedish mine. (Drdmann, Edv. Stalagmit och pisolitartade 

 bildningar i Hoganas stenokolsgrufa, Shone. Geol. Foren Forhandl., Stockholm, vol. 24, 

 1902, pp. 501-507, 5 pho. reps.) The illustrations show well the formation of irregular 

 pisolites by dripping calcium carbonate (CaCOs) bearing water (HoO). 



No. 2813.— PROCEEDINGS U. S. NATIONAL MUSEUM. VOL. 76. ART. 16 

 61543—29 2 



