35

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coloured black by organic matter. In these kaolin beds crystals and bunches of crystals of bright, untarnished iron-pyrites occur. On the new wagon-road to Whangaparapara the cuttings show beds of kaolin, soft and unctuous in one place, with a gradual change, until further on the clay has been metamorphosed to a white flinty porcelanite and chert. The bulk of the rock composing the white cliffs on the north, east, and west sides seems to be of this jasper-porcelanite, the south side being mostly sooriaceous trachyte. The porcelanite sometimes contains small nodules of kaolin and pyrite, and with which sulphide of silver has been seen. Almost any of the rock will give by fire-assay traces of silver and gold. One assay by the writer gave 2'l oz. silver and 006 oz. gold to the ton. The baked clays are stratified in beds, the planes of stratification usually falling away from the hill. They rest unconformably on the eruptive rocks beneath. Through the clay beds dykes of trachyte have made their appearance. The heat from the dykes, and perhaps from laccolites beneath, has baked the clays. At a lower elevation on the hill, excavations have disclosed a dark-grey porphyritic rock which quickly decomposes on exposure to the air. The disintegration of this rock will account for the formation of the clay beds. " The top of Te Ahumata is about half a mile in diameter, with the south-east portion the lowest. Around the rim rock shows in place. The central portion is little lower than the edges, and is covered with rock dSbris and mud. A number of holes, probably fumaroles, were noticed. Obsidian and pumice are common on the surface. Large quantities of kauri-gum have been dug on top of this hill in years past, and gum-diggers still work there ; but there are no large trees within 400 ft. of the top of the hill. " The only mining being done on the Barrier is on the Great Barrier and on the Barrier Eeefs Claims, which are adjoining properties, and working on the same reef. This reef ha,s been named the Lee Reef. The workings on the Lee Reef are about half a mile north-west from the summit of the hill The Lee Reef has a strike nearly magnetic east and west, and a dip to the south of 70 deg. It has been developed in the two properties by drifts along its strike for nearly 1,200 ft., and in that distance no faulting has occurred, and there has been but little change in its general direction. The workings of the Great Barrier Company on this reef consist of two levels, about 90 ft. apart. The end of the upper drift is about 600 ft. from the boundary-line between the Great Barrier and Barrier Reefs. The mouth of the drift or adit is a few feet from the boundary. A cross-cut tunnel, about 200 ft. long, connects the low level with the surface. The low level is being extended eastward, and the face is over 200 ft. from the" boundary-line. The ore being taken out is good-looking quartz. " The workings of the Barrier Reefs consist of an upper level driven on the reef for 150 ft. The mouth of this drift is about 80 ft. from the entrance to the upper drift of the Great Barrier Company, and is on the same level. A creek between the two shows the reef exposed on the surface. Near the creek a shaft was sunk 214 ft., and a cross-cut was made to the reef. The low level is now being extended eastward to join this cross-cut. The low-level workings consist of an adit 1,050 ft. long, and about 500 ft. of drifting on the reef. The reef was cut 700 ft. from the mouth of the adit, but the cross-cut was continued until another reef was cut in the present face of the adit. " The Lee Reef has varied in width from 8 in. to 6 ft., but is usually between 18 in. and 3 ft. in width. The reef is a fissure vein in a dark basic eruptive rock, probably diorite. The diorite is usually decomposed and bleached on one wall or both, but in places it is aphanatic, with the quartz frozen to both walls. The country to the north and south from this sheet of diorite, as exposed in the cross-cuts, appears to be an andesite. The ore shows a ribbon structure. There is usually a rib of white quartz in the centre of the vein, with a band of richer ore on each side. In the vicinity of a ' horse' the Vein is usually brecciated, with the angular fragments of country rock partly or wholly replaced by ore. The surface ores are high-grade in silver in the form of sulphide, mostly stephanite and polybasite, with some pyrargyrite and. proustite. On the surface, in places, assays can be taken of samples across the reef giving over 400 oz. in silver to the ton, besides good values in gold. With depth the percentage of silver in the ore has decreased, and that of gold has increased. Some high-grade gold-ore has been taken from the low-level, without enough silver in it to part the assay-button. The gangue is white quartz, with a little calcite and some kaolin. A small percentage of iron-pyrites, with traces of copper-pyrites, and occasionally mispickel, are to be seen in ores from the low levels. No lead, bismuth, or tellurides have been noticed. Gold never shows in the ore, and no prospect can be had in the pan, but the pan-concentrates contain nearly all the gold. The water from the reef contains a small amount of sulphuretted hydrogen, and this, together with the alkaline carbonates, will account for the presence of gold in the reef. Besides the calcite in the reef, there are parallel seams of calcite on each side in hanging- and foot-wall country. " A number of other reefs show on the surface, some of which have been cut by the underground workings in these properties, but no development-work has been done on them. These reefs have different strikes and dips, some running nearly north and south. The north-and-south reefs are older than the Lee Reef, as shown by the Lee Reef intersecting them. Some of the large reefs contain stibnite. A brown precipitate from the waters from one of them, tested qualitatively, showed iron, antimony, and traces of arsenic. " On the opposite side of the hill, half a mile south from the Great Barrier-Barrier Reefs workings, is the Barrier Proprietary. Near the surface on this property a body of rich silver-ore was taken out and shipped. The reef has an east-and-west strike, and a dip to the north—the opposite to that of the Lee Reef. In view of the experience on the Lee Reef, it is possible that sinking on the Proprietary Reef might show an increase in gold-values sufficient to warrant development. " The lona-Aotea properties have cross-cut tunnels on the north side of the hill, near the contact of the sinter deposit. A little driving has been done from both cross-cuts. The lona reef seems to be of the same character as the sinter cliffs above, with the difference that in places there appears to be more vitreous quartz showing in the stone. From some of the stone containing this glassy quartz the writer saw very good pan-prospects obtained. There is a chance of getting a rich body of ore on these properties in the vicinity of the contact. 6—C. 3.