2 FiKM) Museum of Natural History 



lines of coal mines have developed a nomenclature of 

 their own for many of these features. 



The mine represented in this model is a small one 

 in a vertical vein in hard rock. The rock is very firm 

 at the left near the shaft and becomes less solid to the 

 right, where the vein is intersected by another one in a 

 weaker and more broken rock which tends to cave and 

 fill any openings made in it. The mine is in a region 

 where timber is expensive and where there is but 

 little water. Electric current developed by water 

 power is available for power. The methods of mining 

 employed are those suited to these conditions. 



The vein forms the entire vertical front of the 

 model. Its intersection with the surface of the ground 

 is its OUTCROP. Near the shaft and for the greater 

 part of its length, the outcrop is covered by soil. 

 Towards the right of the model the outcrop of the 

 vein appears above the soil in two places, where it can 

 be distinguished from the surrounding rock by its 

 darker color. This dark brownish-red color is due to 

 the presence of large quantities of oxides of iron which 

 are residues left from the destruction by weathering 

 of some of the original vein minerals. Such an iron- 

 stained outcrop is called an IRON HAT. 



Not all veins develop an iron hat, but most of 

 them present at their outcrops color contrast with their 

 surroundings by which they may be readily traced 

 wherever they are not covered by soil. 



THE ORE in the upper part of the mine is a 

 weathered and iron-stained quartz. The values lie in 

 minute particles of free gold disseminated through 

 this quartz. In the lower levels this ore is replaced, 

 as is usual in such deposits, by a cleaner quartz, which 

 contains no free gold, but encloses quantities of the 

 sulphides of the heavy metals, principally iron and 

 copper. The two principal sulphides in this vein are 



[2] 



