422 GEOLOGICAL NOTES, 



(2) Next in age are diorites, which have intruded the preceding 

 rocks in the shape of dykes and laccolites. The diorite varies in 

 texture from crystalline-granular to crypto-crystalline, and in 

 colour from greenish-grey to dark blackish-green. At "The 

 Falls," above the Junction Mine, is pi'obably one of the most 

 magnificent sections illustrative of laccolitic intrusions to be seen 

 in New South Wales. An immense dyke of diorite is here seen 

 to have intersected the claystones almost vertically, and at 

 intervals of from a few inches to about twenty feet it has 

 extended itself laterally along the planes of bedding of the clay- 

 stones in sheets of from J-inch to about 20 feet in thickness, and 

 from a few feet to over 100 yards in length. At first sight the 

 precipitous hill-side here appears to be composed of alternate beds 

 of eruptive rock and altered sedimentary strata, at first mistaken 

 by the author for a volcanic series of lavas alternating with fine 

 tufis. A closer examination, however, convinced Mr. Stonier 

 and the author that these apparent beds were in reality intrusive 

 laccolites, as evidenced by the slightly intrusive character of tlie 

 junction line of their upper and under surfaces with the sedi- 

 mentaries, their unbroken continuity with the diorite of the large 

 dyke, the abundance of hornblende in them, and lastly the 

 development of small light grey spots in the claystones near the 

 point of contact, due probably to the formation of chiastolite. 

 In places the laccolites have brought about a partial solution or 

 fusion of the intruded sedimentaries, and where they pass into the 

 so-called ore beds the author thinks they have intruded and 

 replaced probably beds of limestone, absorbing into themselves 

 the lime so as to form a type of rock of an ultra-basic character, 

 for which perhaps the term Manduramite may be suggested. 

 This Manduramite consists of a coarsely crystalline admixture 

 of calcite and primary hoi'nblende with perhaps some felspar, and 

 abundant magnetic, arsenical, and iron pyrites, with a little 

 copper pyrites. It occurs in lenticular masses from a few feet 

 up to 20 feet thick. The junction line of the Manduramite with 

 the claystone is clearly an intrusive one, the claystone being much 

 bleached and altered into a whitish jasperoid rock at the points 



