257 
THE SOUTHERN EXTENSION OE THE DYKE FOUND IN 
THE UNION MINE, DIAMOND CREEK. 
Bv A. M, Howitt . 
The main reef workings in the Diamond Creek district are along a 
felspathic dyke, as described in a report on the Union mine by Mr. E. 
J. Dunn, F.G.S., in the Records of the Geological Survey , Vol. II , 
Part I. 
At the Union mine the reef and dyke have been worked some distance 
South of the shaft, and specimens of the dyke rock were found near the 
old South shaft, close to the south-west corner peg. South of this the 
dyke has not been definitely traced. A decomposed igneous rock of more 
basic character than the Union dyke, and probably more recent in age, 
occurs in an old tunnel about io chains north of the Allendale tunnel; and 
in a shaft a few chains away a basaltic rock was cut, which may have 
some connexion with that in the tunnel. 
Going south through allotment D, Sec. XVI., the Allendale reef is 
met with; it is one of those reefs locally called a “ diagonal,” that is, a 
quartz vein formed along a fault that displaces the dyke. Years ago this 
reef was mined by a number of shafts ranging from 30 feet to no feet 
deep, and in more recent years by a tunnel 290 feet long and other works. 
The strike of the reef is about N. 20° E., and its dip is from 
westerly to vertical. The strata also strike east of north. 
Two ounces of gold to the ton is stated to have been obtained near 
the surface, but crushings taken out about ten years ago from deeper 
workings gave the following yields :— 
8 tons—18 dwt. per ton. 
13 tons—1 oz. per ton. 
7 tons—16 dwt. per ton. 
The stone, which was laminated and nicely mineralized, averaged about 
4 inches wide, reaching a greater thickness as bulges were met. A 
mineralized body of stone, about 1 foot thick, was mined but not 
crushed, and several tons of it are now showing on the dump. No dyke 
was found. 
The last shaft on the Allendale line of reef is in allotment B, Sec. 
XVI. South from this point the main felspathic dyke could not be 
traced owihg to the soil obscuring the underlying rocks, but I am of 
the opinion that it is not far south of the last Allendale shaft. In allot¬ 
ment B, Sec. XI., the dyke does not outcrop; in allotment D, Sec. 
XI., it outcrops for some distance but lies to the west of its course when 
last seen, at the surface near the Union mine. The dyke walls cannot be 
examined from the surface, but from the trend of the outcrops it is 
probably very wide, underlays to the east, and strikes N. 15° W. 
The outcrops and veins of quartz along and adjacent to this southern 
extension of the main felspathic dyke are worth the attention of 
prospectors. • 
From this geological examination it appears that across the Diamond 
Creek from the Union mine the main Diamond Creek dyke has been 
faulted to the west, going south, by one or several separate movements; 
and one of these movements may have been more extensive and possibly 
along the Allendale reef “ diagonal.” (See plate XLIII.) 
I examined the country to the east of the creek as shown on the plan, 
but could discover no 'outcrops of dyke rock on that side. 
[z 7.7.08.] 
