CHAPTEPt IV. 



THE BASALTS. 



Section I. — The Meteoric Basalts. 

 Variety. — Basalt. 



Slanncrn, Moravia. 



TscHERMAK has described the Staimerii meteorite as a granular rock, showing an 

 evident fragmental structure. According to him, it is not a homogeneous crystalline 

 rock, but oue composed of rock fragments of three different kinds : coarse-grained frag- 

 ments, radiated fiuer-grained fragments, and compact fragments. 



The coarser-grained fragments are chiefly composed of anorthite lamina? and augite 

 columns united together. Some of the anorthite crystals show very fine twinning, but 

 most have broad twin lamina3 which are sometimes bent. Besides tlie colorless anorthite, 

 and the brown to blackish augite, Tschermak observed a colorless isotropic mineral, which 

 is probably the same as the mineral he had described as an isotropic labradorite (maske- 

 lynite) from the Shergotty meteorite. Minute grains of chromite, iron, and pyrrhotite 

 occur inclosed between the other minerals ; and black forms were seen in the augite. 



The fragments, of an e\'idently radiated texture, are composed of anorthite laminne 

 interspersed with augite needles. Black grains occur in these fragments. 



The compact fragments formed a gray mass, which in several points showed a radiated 

 fibrous structure, and which contained the before-mentioned black grains. 



The groundmass which unites these fragments is composed of anorthite and augite 

 grains, and black particles.* 



Tschermak later stated that this meteorite was closely like that from Juvenas, but finer- 

 grained ; but it did not contain either the unknown silicate or pyrrhotite found in i hat.f 



The specimens of this rock in the Harvard College Mineral Cabinet, resemble in 

 structure, on macroscopic examination, some diabases, but are of a much finer grain ; 

 the general crystalline arrangement is the same. 



Constantinople, TurJcef/. 



The Constantinople meteorite was found by Tschermak to be an ash-gray, neai-ly 

 compact rock, composed of compact small fragments and fine radiating masses. 



It was seen under the microscope to be composed of anorthite, pryoxene, pyrrhotite, 

 and chromite. Its microscopic structure agrees with the Stanneru meteorite, as also iloes 

 its chemical composition.^ 



* Min. Mittli., 1872, pp. 83-85. f Die mikros. Bcscli. dor Metcoriten, 18S3, i. 7. 



X Min. Mitth., 1872, pp. 85-87. 



