ECLOGITES IN CALIFORNIA 345 



Hitherto, so far as known to the writer, no rocks have been described 

 in the country under the title of eclogites. Nutter and Barber^ refer 

 to them incidentally in their discussion of glaucophane schists, and 

 Diller^ has recently included some rocks of the eclogite type in his 

 description of the amphibole schists of Port Orford, Ore., but without 

 designating them by this term. A brief prehminary review of the 

 eclogites of Europe will furnish a basis for comparison in the study 

 of those of our west coast. 



EUROPEAN ECLOGITES. 



The type eclogite of Europe is described in the valuable paper of 

 Ludecke,^ who gives a detailed account of the chief minerals and of 

 a dozen rocks found in the island of Syra. Of these latter he places 

 glaucophane eclogite as the most important. This consists of red 

 garnets, light green omphacite, and. glaucophane. He mentions 

 muscovite, quartz, and pyrite as accessory minerals. The omphacite 

 is a light green augite appearing in grains and in small columns, 

 sometimes showing the augite cleavage. Under the microscope there 

 is little or no pleochroism, bright polarization, and a high extinction 

 angle. The garnets are rhombic dodecahedrons w^ith rounded cor- 

 ners. The glaucophane is the same as that so common on the 

 Pacific coast, and which will be described more fully later. The 

 garnet is considered the oldest mineral; younger than that is placed 

 glaucophane and omphacite; and youngest of all, the quartz. In the 

 laboratory at Stanford University are small specimens of the Syra 

 eclogite — obtained through the kindness of Mr. Diller — which very 

 much resemble some facies of the glaucophane eclogite of Tiburon. 

 The glaucophane is a trifle darker blue, and the garnets do not show 

 such definite crystal forms as do those in the California rock. In 

 his general description of eclogites Lohmann reports the occurrence 

 of the rock in Norway, Switzerland, Austria, France, Italy, Greece, 

 and South Africa. Lohmann's paper is mainly devoted to an account 



1 "On Some Glaucophane and Associated Schists," Journal of Geology, Vol. 

 X, p. 738. 



2 Folio No. 89, Geological Atlas 0} the United States. 



3 "Der Glaucophane und die glaucophane-flihrende Gesteine der Insel Syra," 

 Zeitschrijt der Deidschen Geologischen Gesellschajt, Vol. XXVII (1876). 



