VEIN MATERIALS OF FRYER HILL. • 451 



Gangue. — The material which replaces the limestone on Fryer Hill does 

 not differ essentially from that already described on Iron and Carbonate 

 Hills. It is mainly an impure mass of oxides of iron and manganese, with 

 a greater or less admixture of silica and clayey materials. It differs some- 

 what in different portions of the hill, being relatively richer in alumina and 

 iron in the main mass of the hill, and very silicious in the eastern portion, 

 or in the Lee group of mines. The black or manganiferous iron, which 

 forms a large portion of it, though very irregular in its distribution, is, as 

 elsewhere, generally barren. In the main mass of the hill silicious replace- 

 ments consist of black chert, often forming large, nln.ost solid bodies and at 

 other times being thoroughly shattered into angular fragments, the seams 

 more or less filled with clay. Considei'able amounts of sulphate of baryta 

 in crystalline form are scattered irregularly through the ore deposits, and 

 are generally considered a good indication of ore, inasmuch as they usually 

 accompany rich masses of chloride. The oxide of iron is generally hy- 

 drated, though sometimes mixed with a certain amount of anhydrous oxide. 

 Frequently it forms a comparatively pure iron ore and is valuable as a flux, 

 notably that occurring in the Amie mine, From this, with varying propor- 

 tions of iron and silica, it passes through jaspery iron with conchoidal fract- 

 ure into almost pure silica. It is frequently cavernous, the cavities being 

 lined with crystals of quartz, cerussite, and sometimes of pyrolusite. Black 

 iron contains from 10 per cent, of manganese upwards, though never ap- 

 proaching a pure manganese mineral in any large quantity, except in the 

 Dunkin and in the adjoining workings of the Climax No. 3. No pyrites, 

 so far as known, have ever been found in the mines and carbonate of iron 

 is extremely rare. 



Ore deposits. — Ore occurs either in the form of galena or its decomposi- 

 tion products, carbonate and a little sulphate of lead, with a small amount 

 of chloro-phosphate or pyromorphite ; and silver, either inclosed in the 

 galena or impregnating the vein materials in the form of chloride, chloro- 

 bromide, or iodide, or a mixture of the three. Galena occurs irregularly, 

 generally in the center of a large mass of vein material, with its surface 

 more or less oxidized and changed into carbonate. Besides this, considera- 

 ble masses of sand carbonate with hard carbonates are found, which are 



