A rotary percussion drilling programme (8 vertical holes for a total penetration of 1920 feet) was undertaken at Netley Hill to look for economic copper and molbdenum mineralisation in a greisen (hydrothermally altered granite) body which has an associated surface rock chip and stream sediment geochemical anomaly of up to 100 ppm Mo, although no molybdenum minerals outcrop as they do nearby at Anabama Hill, and only trace surface indications of copper mineralisation (turquoise) can be seen. The drilling established the presence of molybdenite and chalcopyrite at depth within a large mass of greisen, below the zone of oxidation and weathering. Best downhole assay results were 760 ppm Mo from the depth interval 210-220 feet in hole NET/RP2, and 5700 ppm Cu from the depth interval 220-230 feet in hole NET/RP3. It is believed that the alteration process has basically involved the introduction of silica and pyrite plus dissolved molybdenum and copper. Early in 1970 a ground magnetic survey was conducted on a 100' x 500' grid laid out over the alteration complex exposed at Netley Hill, in order to try to extrapolate different rock-types from the outcrop outwards beneath alluvium. The results proved inconclusive as the various rocks could not be magnetically discriminated, so Asarco resorted to detailed, 1:6000 scale geological mapping to determine the distribution of disseminated mineralisation in the transition zone between granite and greisen. To help determine the controls on apparent localised copper concentrations found by the mapping, and to test some interesting low order magnetic anomalies that in part correlate with the best grade subsurface mineralisation intercepts previously recorded, 9 additional vertical rotary percussion drillholes totalling 2021 feet were completed. The results of this drilling were disappointing, with only trace of molybdenum and copper intersected. Some supergene enrichment of molybdenum and copper has occurred, but it is not extensive. Turquoise is the most abundant copper mineral encountered within the zone of weathering. Pyrite is the most abundant sulphide, occurring below the zone of weathering in both altered and unaltered granite. It appears that a volume increase in pyrite is usually accompanied by increased copper content, but the same relationship does not always apply for molybdenum. In altered granite the weathering profile is deep (to at least 230 feet in hole NET/RP11) and clay is common. The abundance of limonite-goethite filled cavities, limonite pseudomorphs after pyrite cubes, turquoise, and the occasional boxwork structure, attest to a period of secondary leaching. Apatite found in the altered granite is thought to have been a source of phosphoric acid contributing to the abundance of turquoise, which has replaced feldspar grains. The turquoise occurs as low angle veinlets, within quartz veins along with magnetite, and exists in all moderately altered rocktypes except quartz porphyry. Due to the sub-economic nature of the mineralisation seen in a sufficently widespread drilling coverage at Netley Hill, the presence there of any large base metal orebody is much doubted, and therefore it was decided to surrender tenure.