174 BULLETIN 42, UNITED STATES NATIONAL MUSEUM. 



Zincite occurs ouly iu Sussex County, New Jersey, and is used largely 

 to make zinc oxide for j)aints and other purposes. 

 To represent the occurrence of zincite two specimens are shown : 



(1) Massive, with Fraukliaite aucl willemite. Miuc Hill, Fraukliu, Sussex Couuty, 

 New Jersey. (17(334.) 



(2) Massive, with Frauklinite aucl calcite. Mine Hill, Frankliu, Sussex Couuty, 

 New Jersey. (6.5310.) 



FRANKLINITE. 



Composition: (Fe, Zn, Mn) (Fe, Mn)204. Oxides of zinc, iron, and 

 manganese, containing variable amounts of earth metal. 



It crj' stallizes in the isometric system, especially in octahedrons, with 

 modifying faces; also occurs crystalline, granular and compact. It 

 varies in hardness from 5.5 to 6.5, and has a specific gravity of 5. It 

 has a full metallic luster and iron-black color. It is slightly magnetic. 



Frauklinite is found very abundantly at and near Franklin, New Jer- 

 sey, whence its name. The zinc it contains is extracted iu the form of 

 oxide for use as a paint, and afterwards the iron and manganese are 

 smelted into spiegeleisen. To represent the occurrence of frauklinite 

 three specimens are shown : 



(1) Crystallized, iu octahedrons, iu calcite. Buckwheat vein, Frankliu, Sussex 

 Couuty, New Jersey. (1763R. ) 



(2) Crystalline grains, iu calcite. Buckwheat veiu, Fraukliu, Sussex Couuty, New 

 Jersey. (65311.) 



(3) Crystalline grains, cemented by zincite. Sterling Hill, Franklin, Sussex Couuty, 

 New Jersey. (4802.) 



SPHALERITE. (ZINC BLENDE, BLACK JACK.) 



. Composition: ZnS. Sulphide of zinc, containing zinc 67 per cent, 

 and sulphur 33 per cent. 



It crystallizes in the isometric system, crystals being complicated and 

 commonly twinned. It frequently occurs as a coating, sometimes 

 fibrous ; it also occurs massive. It varies in hardness from 3.5 to 4 

 and in specific gravity from 3.9 to 4.2. It has a full resinous luster 

 and occurs in a large variety of colors, from colorless to black, the most 

 common colors being yellow and brown. It is generally transparent, 

 though sometimes ouly translucent. It has a highly characteristic 

 dodecahedral cleavage. 



Blende is a very common and abundant ore of zinc; but it is onh' 

 recently that it has been much utilized, as it requires careful roasting 

 to remove sulphur previous to the extraction of the zin(;. It is gener- 

 ally associated with other sulphides and very frequently' contains silver. 



Blende yields very easily to decomposing influences, but, since the 

 sulphate, which is apt to be formed first, is very soluble in water, the 

 products of decomposition are generally removed as fast as formed and 

 the zinc deposited elsewhere, generally after undergoing farther 

 changes. Sometimes, however, it is changed directly in place to the 



