458 REPORT OF NATIONAL MUSEUM, 1896. 



The latest effort was that made by Mr. A. Sjogren, a learned Scandina- 

 vian geologist interested iu prehistoric authropolgy, acquainted with 

 the imi)oitance of the "jade question," and always on the lookout for 

 any evidence that would sheti light tliereon. He resided for a time in 

 Costa Eica, with full opportunity for the investigation of and acquaint- 

 ance with the jadeite objects in that country. During his visit there 

 he made more or less extensive searches for the evidence of indigenous 

 jade. He found a number of pebbles the appearance of which sug- 

 gested that they might be the desired material. Ou his return to his 

 native country he stopped at Washington, and, visiting the United 

 States I^ational Museum, he invoked the aid of Professor Merrill, 

 Curator of Geology and Mineralogy, and the author, as Curator of 

 Prehistoric Anthropology, who opened the cases in his department and 

 produced implements from Costa liica and the neighboring countries 

 for comparison with the specimens trought by Mr. Sjogren. The 

 result was that eight specimens of pebbles were selected as having the 

 greatest similarity with the material of the jade implements, and it was 

 proposed to put them to test of microscopic investigation. Professor 

 Merrill accordingly made thin sections of these for that purpose, and 

 has just reported the result of his investigations. He says: 



Nos. 1, 3, and 8 are without doubt an altered pumiceous tuffa, identical with No. 

 59899, described by Professor Clarke and myself iu our paper iu Proceedings of the 

 United States National Museum, Vol. xi, page 127. 



This specimen (No. 59899, U.S.N.M.) was from San Huacas, Costa 

 Rica, dark green, not mottled, soft, specific gravity 2.282, and its com- 

 position as follows : 



Ignition 10.39 



Silica 70.49 



Alumina 11. 39 



Ferrous oxide 2. 39 



Manganous oxide .Trace. 



Lime 3. 83 



Magnesia 57 



Alkalies Undetermined. 



Total 99.06 



A microscopic examination shows that the mineral is evidently a highly altered 

 volcanic tuff, but very difficult to make out. The mass of the rock is made up of a 

 greenish-gray amphorous felt, through which are scattered round buuches of a 

 bright-green chlorite and small, colorless points and elongated crystals, which may 

 be felspathic, although they are too small to show twin striie. There are also occa- 

 sional colorless elongated and curved shreds, which are wholly without action in 

 pohirized light, and which are doubtless glass. 



He continues as to the Sjogren specimens: 



Nos. 2, 4, 5, and 7 are highly siliceous rocks of rather obscure nature, but consisting 

 largely of chnlcedouic silica, and if not true chalcedonic secretions, are at least 

 very compact Iragmental rocks that have been acted upon by silica-bearing solu- 

 tions. No. 7 shows occasional niiuuto circular areas with concentric structure, 



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