USEFUL MINERALS. 585 



7. Sulphate of Barytes occurs in small crystals lining fissures, and 

 in compact veins in the ankerite. Though quite insoluble, this sub- 

 stance can be decomposed by heated solutions of alkaline carbonates ; 

 and when these are cooled it is re-formed and deposited.* It has 

 probably been introduced in this way into this vein. 



I shall endeavour in the following remarks to state the manner in 

 which these minerals occur in the complicated mixture which fills this 

 vein, and their probable origin. Let the reader then imagine that he 

 is standing on the side of the deep ravine of the Great Village River, 

 looking into a rocky excavation in which the minerals above mentioned 

 appear to be mixed together in the most inextricable confusion, in 

 great irregular cracks of the slaty rocks, and he will be able, perhaps, 

 to wade through the following description. 



The ankerite should evidently be considered the veinstone, as it 

 surrounds and includes all the other contents of the vein, and greatly 

 exceeds them in quantity. Where not exposed, it is white and coarsely 

 crystalline. On exposure it becomes yellowish ; and near the surface, 

 as well as on the sides of fissures, it is decomposed, leaving a residue 

 of yellow ochrey hydrous peroxide of iron. In some parts of the vein, 

 the ankerite is intimately mixed with crystals and veinlets of yellowish 

 spathose iron. The red ochrey iron ore occurs in minor veins and 

 irregular masses dispersed in the ankerite. Some of these veins are 

 two yards in thickness ; and the shapeless masses are often of much 

 larger dimensions. Specular iron ore also occurs in small irregular 

 veins, and in disseminated crystals and nests. At one part of the 

 bank there appears to be a considerable mass of magnetic iron ore, 

 mixed with specular ore ; this mass was not, however, uncovered till 

 after I had left the ground. 



The whole aspect of the vein, as it appears in the excavations in 

 the river-bank, is extremely irregular and complicated. This arises 

 not only from the broken character of the walls, the included rocky 

 fragments, and the confused intermixture of the materials of the vein ; 

 but also from the occun-ence of numerous transverse fissures, which 

 appear to have slightly shifted the vein, and whose surfaces usually 

 display the appearance named " slickenside," and are often coated 

 with comminuted slate or iron ore. In some places these are so 

 numerous as to give an appearance of transverse stratification. One 

 of them was observed to be filled with flesh-coloured sulphate of 

 barytes, forming a little subordinate vein about an inch in thickness. 



The general course of the vein, deduced from observations made by 

 Mr Hayes and myself at the Acadia Mine and further to the eastward, 

 * Bischoff, quoted by De la Bcchc. Gcol. Obs. p. 6G9. 



