Blackhead Quarry, Dunedin City, Otago Region, New Zealandi

Regional Level Types
Blackhead Quarry	Quarry
Dunedin City	City
Otago Region	Region
New Zealand	Country

This page is currently not sponsored. Click here to sponsor this page.

PhotosMapsSearchMineralogy

Blackhead Quarry is an active aggregate quarry approximately 8 kilometres south-east of the Dunedin city centre.

Zeolites have been collected by local rock clubs, who at times have been given permission to fossick in the quarry. The zeolites occur in vesicles in the upper layer of the quarry, however as this has been largely mined out, specimens have become increasingly difficult to find. Much more of the headland has gone from mining since the 1995 photographs listed on Mindat, although the columnar basalt structures at the edge of the headland are protected under a covenant. While vugs up to 30 cm wide were found in early fossicking, most of the specimens now are micro.

Quarrying started in the 1950s, and since 1986 has been a joint venture between Palmer and Son Limited, and Fulton Hogan Limited. Around 120 000 tonnes of aggregate is produced per annum.

Blackhead was formed around a peripheral volcanic vent, as part of the Miocene Dunedin Volcanic Complex. Rocks show as pale grey basaltic lithic tuff on the north side of the quarry, with pale grey crystal tuff elsewhere. The upper parts of the deposit was highly vesicular (50-75%) within splatter cone material, containing abundant zeolites. Natrolite, phillipsite and calcite are the most common species within vesicular basanite. Chabazite and thomsonite is restricted to the north-east part of the quarry, while gismondine was only found in one small area below the natrolite bearing zone.

Natrolite is found as glassy to colourless to white hemispherical aggregates of prismatic crystals, commonly from a gonnardite centre. The crystals may be coated with montmorillonite as botryoidal aggregates.

Phillipsite in three different habits as 1) glassy short prismatic fourling crystals forming dense aggregates lining basanite, some associated with siderite and clay altered basanite; 2) dense matted tiny crystals or botryoidal aggregates up to 2mms long coating the walls of vesicles; 3) glassy crystalline equant crystals lining basanite.

Calcite is found in variety of habits, however multiple habits are not found in each vesicle. It is often found associated with the zeolites. Calcite crystals range from 0.1 to 2mm long, transparent to colourless, opaque to white. 1) as glassy colourless massive crystalline; 2) glassy colourless nail head crystals on a thin siderite lining 3) colourless glassy complexly twinned rhombohedral crystals associated with emerald green chlorite, as linings on siderite on massive basanite, or within the basaltic tuff; 4) glassy colourless schalenohedral crystals on a crust of tiny phillipsite crystals lining siderite in massive basanite; 5) colourless glassy cloudy and clear zoned simple rhombohedral crystals up to 2mm long.

Olivine as olive green transparent to translucent crystals. Thomsonite as thin glassy colourless to dull silky white well terminated bladed crystals to 1 mm long. Gonnardite as 1) pearly white centres to 10 mm diameter within natrolite aggregates on massive basanite; 2) glassy colourless on phillipsite and natrolite 3) as white hemispherical hollow aggregates or radiating sprays as thin elongated prismatic crystals, with overgrowth of colourless glassy natrolite.

Commodity List

This is a list of exploitable or exploited mineral commodities recorded at this locality.

Mineral List

11 valid minerals.