History – The Mabbett collection

As you wander down the corridor toward the museum’s Wilson Cement Works exhibition, an amber glow to your left catches your eye. Inside a glass case, a carved chalcedony owl sits on a tree standing sentinel, poised above a miniature forest of agate. Surrounding this scene are stained glass panels of agate slivers, filtering the light into honeyed tones. This tableau forms the top shelf of the display cabinet that houses the Berkeley Frank Mabbett collection of gemstones and fossils.

The collection is remarkable for its diversity of gemstones, petrified wood and fossils, and the fact that they were all found on Berkeley Mabbett’s farm on Kaipara Flats Road. Berkeley’s son Rob remembers that in the early farming days the main deposit of rocks had been used to build up the cow yard, to infill the driveway and at the end of the culverts. It was common practice in farming to use resources that were on hand, and as the rocks were hard, they were fit for purpose.

The cultivation of land and the removal of top soil in farming can often expose geological features, and the main concentrated deposit of rock at the Mabbett farm was discovered in exactly this way. When Berkeley was clearing a hill area for planting in pasture he noticed scattered rocks hitting the blades of the discs, which on first appearance had the dull white powdery coating of kauri gum that the children would collect and sell for pocket money. However, these rocks were a lot heavier than the gum that was collected and inside they revealed a variety of gemstones. Included in the Mabbett collection display case are moss agates, pink agates, jasper, quartz and even amethyst.

The discovery of quartz (an indicator of the potential for gold) resulted in the building of a gold mine on the property during the late 1800s. However, like other gold mines in the Mahurangi area, this one proved to be uneconomical and was abandoned. Rob Mabbett remembers discovering the old gold mine, with its shaft lined with totara timber that had been split by hand and held in place by carved pegs inserted in drilled holes at the corners. Rob also discovered the large concretion that sits on the lower shelf of the cabinet, alongside what is thought to be the remains of a fossilised Moa egg.

Two similar rock deposits were also found on the property, with one located in soil around a spring in a gully, which was revealed when the gas line was put through to Warkworth, and another next to where the farm race descended the hill.

With an interest in lapidary Berkeley obtained a mineral licence in the 1970s to cover the area of the farm where the deposits were located. He went about building his own equipment for processing the stones into cabochons and jewellery to sell. A collection of cabochons in a variety of colours and patterns is on display in the cabinet along with the cut stones from which the jewellery was made. Berkeley continued his lapidary hobby up until the 2000s using rocks he had collected from these deposits over the years.

If you are interested in the geology of the Mahurangi area and the impact it had in seeding local industries, pop into the museum and visit the fascinating Berkeley Mabbett collection, along with our exhibition of the Wilson Cement Works, underpinned by Mahurangi limestone, and the copper mining of Kawau Island.