VICTORIAN STATE COAL MINES. 375 



Any coal at a depth of less than 50ft. is usually very 

 friable, but all coal beyond that depth is much firmer, although 

 boring- shows that it is not correct to assume that the greater 

 the depth the better quality of coal. 



Three bores have gone down 1158ft., 2633ft., and 1380ft. 

 respectively in search of lower seams, but without meeting 

 anything of a payable nature. 



The coal-bearing rocks throughout the State Mine area 

 are marked by recent deposits of sands and clays, seldom 

 exceeding 30ft. in thickness. The surface consists largely of 

 dunes of blown sand and swamps, in which peat deposits are 

 now accumulating. From a study of the boring records it 

 appears that the present surface deposits now being formed 

 are of a somewhat similar character to some of those that were 

 deposited contemporaneously with the Wonthaggi coal seams. 



The most important geological features from, a mining 

 standpoint are the faults or vertical displacements that occur 

 throughout the Victorian coal measures. These faults may 

 vary considerably in displacement, sometimes dying out to 

 nothing at one or both ends, while the maximum vertical dis- 

 placement often exceeds 100ft., and in the main fault lines 

 considerably more. As far as the present workings are con- 

 cerned it has been found that the faults usually run approxi- 

 mately at right angles following the cardinal points of the 

 compass. These faults have the effect of cutting the coal area 

 into a series of plateaux. 



Boring has been done at fairly close intervals ahead of 

 the State Mine workings, and the data obtained has been 

 utilised in constructing a model showing the lie of the coal. 

 By this means shaft sites can be selected and an idea formed 

 in advance of how the workings should be laid out. Over the 

 ground worked to date it has been found that the general rule 

 is 'that the coal dips to the south, and when faults occur is 

 down thrown to the north, making a section resembling a saw 

 tooth. These faults act as natural boundaries to the area of coal 

 that can be profitably worked from each shaft, and as the 

 deepest coal yet found on the State Mine Reserve is only at a 

 depth of 500ft., shaft sinking is not a serious item, and it is 

 expected that by selecting shaft sites in suitable positions, 

 dead work will be reduced to a minimum. 



The fault movements appear to be still in progress, and 

 can often be picked up on the surface, thus affording valuable 

 data for prospecting work. 



