THE COLLECTION OF MINERALS 



have gathered many minerals. Most of the species which have 

 been found may be seen in the Collection (Case 27) of the New 

 York Mineralogical Club. This collection is arranged to show, 

 approximately, the minerals of the foliated schistose mica and 

 hornblende rocks, the minerals of the granite veins, dikes and 

 bosses and the minerals of the limestone beds. 



Beginning with the minerals of the mica rocks, very fine ex- 

 amples of a yellow to brown Stilbite are noteworthy, the rosettes 

 of flat blades lying upon the scaly surface of the gneiss or schist. 

 With these are remarkable specimens of Chabazite, Epidote, 

 Fibrolite, Harmotone, Heulandite and the interesting little 

 spheres of Sphaerosiderite. The hornblende rock follows with 

 superb flattened crystals of greenish Titanite imbedded in the 

 black masses. The view taken by geologists of the hornblende 

 rocks on Manhattan Island now is that they are the changed 

 remains of former igneous intrusions, soft pasty lava-like dikes, 

 entering the island beds. They are often associated with epidote. 

 The hornblende rocks are well exposed near 135th Street and 

 Amsterdam Avenue. 



The granite section shows a striking group of minerals, and it is 

 in these granites — mostly veins or dikes— that the collector finds 

 the richer collecting grounds. Here are Allanite (in long crys- 

 tals as Orthite), Apatite, Beryl, Cyanite, Dumortierite (a rare 

 mineral), Feldspars (Albite, Orthoclase, Oligoclase, Microcline), 

 Micas (Muscovite, Biotite), Garnet (note particularly the superb 

 example from West 35th Street), Magnetite, Monazite (a rare 

 mineral containing cerium, didymium, lanthanum and thorium) , 

 Ripidolite, Tourmaline (big, splendid black crystals in Quartz), 

 Wernerite and Xenotime (another rare mineral containing 

 yttrium, erbium, cerium and thorium). 



The last group of minerals belongs to the limestone beds, and 

 here are pretty bunches of Smoky Quartz crystals, brown Tour- 

 malines and white Pyroxene (Malacolite) with peculiar veinlets 

 of fibrous Aragonite. 



Another area (the serpentine) yields examples of an inter- 

 mixture of Calcite (Dolomite) and Serpentine, forming a speckled 

 rock called (incorrectly). Ophiocalcite. More striking specimens 

 of this can be seen in Case I of the Geological Hall. 



There are several mineralogical surprises in the collection, 

 for example: Galenite (sulphide of lead) in minute cubes on 

 Chabazite, Gypsum in radiating prisms on mica rock, Fluorite 

 (large block from the Subway), Iolite (Pinite), Zircon, Uraninite 

 (the chief mineral containing radium). 



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