Middlehurst Station, Marlborough Region, New Zealandi

Regional Level Types
Middlehurst Station	- not defined -
Marlborough Region	Region
New Zealand	Country

In the main flows the basalt is commonly massive with fairly numerous visible crystals of titan-augite and scarcer olivine. Other basalts are finer-grained. Numerous cavities contain zeolites, calcite and quartz. A single flow of white trachyte with a bright-red weathered top forms a conspicuous horizon about 300m below the summit of Mt Lookout and can be traced from the head of Middlehurst Creek for about a mile to the northeast. This rock is mostly oligoclase-andesine and sanidine feldspars with very sparse granular augite in a groundmass of devitrified glass.

No central vent was found and it is likely that all the flows were erupted from fissures now represented by the basalt dikes. Two dikes were seen in Middlehurst Creek that did end in basalt flows. The dikes radiate out from Mt Tapuaenuku, which is a solidified magma chamber, assumed to be the source of the volcanic flows.


Grey chalcedony with inclusions of natrolite crystals and calcite. Colours range from greys, white to pale amethyst. The area is rugged and mountainous.

(Thornton) describes an early visit to the location. No date is mentioned on the source, but the car used to travel to the site dates from the early 1970's. The first location is the track to Mount Lookout, where natrolite is found completely filling cavities, or as a thick lining in the cavities, or in sprays, white or pale pink, clear or opaque. Analcime also frequently lines the cavities under the natrolite, or as separate crystals to 5mm, pale salmon pink. At the highest gate on the Mount Lookout track is quartz and calcite filling fissures in dark fine grained basalt, with analcime, good simple phacolite crystals, and thomsonite as rosettes of colourless clear blades. Some form bulbs, with needles sprouting from it.

Analcime, phacolite, and thomsonite is found on what is named as the Saddle. On the spur near Mount Lookout are vugs lined with phacolite, salmon pink crystalline masses, glassy, rarely a good shape with multiple striations, and tends to crumble.

Mount Upcot is a nearby area with similar minerals. Access is likely to need the station owners permission. It is likely much material remains.

Other Regions, Features and Areas containing this locality

References