74 REPORT 1871. 



On the Aluminovs Iron-ores of Co. Antrim. 

 By Dr. J. Sinclair Hoiden, of Lame. 



These ores have only been discoTered within the last few years, and exhibit a 

 seam both extensive and rich. It lies continuously for about seventy miles along 

 the coast and mouutaiji-glens of Antrim, being nearly horizontally interspread 

 throughout the basaltic rocks which form the floor of the county, and at an average 

 height of 300 feet above the white limestone. 



The elevation above sea-level varies considerably, as among the highest moun- 

 tains it is found at a height of over 1000 feet, from which it gradually falls north 

 and south as low as 200 feet. The general dip of the beds is south-west. 



Dr. riolden gave analyses of the ore, and adds that it is not analogous to any 

 known iron deposit in England, and that basaltic rocks, though containing some 

 iron in their composition, are not generally associated with large deposits of iron- 

 ore. The ferruginous stratum consists of three c[ualities of ore, which, in descend- 

 ing order, are : — •. 



».. Average Metallic Iron 



per cent. 



Pisolite 2 .50 



Bole 8 20 



Lithomarge 30 12 



Total thickness 40 



These graduate into each other. The upper bed, or pisolite, is the richest in iron, 

 and working quantities can be mined containing from 30 to 50 per cent, of metallic 

 iron. 



Large quantities of this ore have now been raised and shipped to England, 

 where it has already made a reputation for itself, i?i facilitating the production of 

 pm'e iron from the siliceous haematites. The entire absence of phosphorus and 

 sulphur, and the presence of a large percentage of alumina, add much to its value, 

 both as an iron-ore and a flux, 



When intermixed with the siliceous ores in the smelting-furnace, the effect is to 

 soften the slag, producing a " loose load," which allows the metal to pass through 

 easily, forming a pure " pig," and, from a given quantity of the mixed ores, deter- 

 mining a higher percentage of metallic iron than could be otherwise obtained. 



It is chiefly used in Lancashire, Cumberland, and South Wales, and is becom- 

 ing a necessity where good steel-iron is demanded. To show that an extensive 

 source of industry has already been developed, it may be stated that upwards of 

 50,000 tons were exported last year, and the quantity will be much greater this 

 year. 



The discovery of this ore has had the effect of stimulating mineral research in 

 the adjoining counties, and Dr. Holden states not in vain, as samples of a good 

 siliceous hsematite have been shown him, and only wait exploration where they 

 were discovered. If found in quantity, no better outlay of capital could be iir- 

 vested than in the erection of smelting-furnaces on the Antrim coast. 



As suggested by the President of the Section, there could be utilized in the 

 local smelting of the ores the large quantity of peat available in the north of 

 Ireland. 



Loealities of Dioptase. Bij Professor N. Story Maskeltne, F.R.S. 



Dioptase has hitherto only been known as a product of the copper-mine at Altyn 

 Tubeh, in the Kirghese steppes of Tartary, if we except certain reputed localities 

 in Germany ; it has been recently met with among old specimens that have been 

 traced to localities in Chili. 



One of these was among the specimens preserved in drawers at the British 

 Museum, which have lately been under careful examination with a view to their 

 identification, and another similar specimen was obtained some years since by 

 W. G. Lettsom, Esq., the well-known mineralogist, from a dealer at Vienna. 



The crystals on both are minute but distinct, and are those of dioptase. The 



