THE COLLECTION OF MINERALS 



shown here (Desk Case i) in sheets like rolled metal; in plates, 

 with crystallized edges ; in braided filaments made up of minute 

 octahedrons; in grouped octahedrons with hollow faces; in 

 twisted plates frequently attached to quartz, around which it 

 curls like some irregular yellow flower. Gold, from an elongation 

 of the octahedron, assumes deceptive forms, while cavernous, 

 skeleton and pitted crystals, peculiar distortions, reticulated 

 and tree-shaped groups with spongy masses and rounded water- 

 worn nuggets are common natural appearances of this precious 

 metal. 



Copper (Desk Case i) is of especial interest, on account of the 

 beautifully crystallized specimens in which it occurs. Most of 

 our specimens have come from the remarkable deposits of Native 

 Copper in the Lake Superior region of Northern Michigan. They 

 exhibit the characteristic crystal forms of the metal, sprigs and 

 branching crystals, twins and massive plates, the common tetra- 

 hexahedron, cubes and superimposed octahedrons. Here will be 

 found also examples of Copper and Silver which have been welded 

 together by nature. 



The next group of minerals is that comprising the Sulphides, 

 Selenides and Tellurides of the metals and semi-metals, and the 

 Arsenides and Antimonides of the metals, which are again suc- 

 ceeded by the so-called Sulpho-salts, in which the union of sul- 

 phur with arsenic or antimony is regarded as an acid, chiefly 

 forming compounds with the bases, copper, silver, lead, iron, 

 zinc and mercury. The great variety and number of mineral 

 species resulting from the combinations thus made possible, are 

 for the most part the source of many useful metals, and these 

 combinations characterize the veins, crevices, fissures, caves 

 and beds of mining regions. 



One of these, Stibnite, the sulphide of antimony, is a valuable 

 ore (Desk Case i ,Wall Case A). This species affords the mineralo- 

 gist very beautiful, lustrous, well-terminated prismatic crystals, 

 usually clustered in radiating groups. The striking specimens 

 here displayed, together with many others which have supplied the 

 cabinets of the world, were found at Mt. Kosang near Seijo, pro- 

 vince of Iyo, Shikoku Is., Japan. In their size and beauty and 



IO 



