Glenstrae Products, Lower Kaimai

by John and Julie Green

The “Powder” factory
Courtesy of the Dickson family

Recent discussion on the Facebook page Tauranga History Online centred around an abandoned industrial site close to the Kaimai School. It is still possible to glimpse the remains (a collapsing Nissen Hut) between the old and new Ngamuwahine Bridges when travelling down the eastern side of the Kaimai on State Highway 29. Several members of the history page offered their opinions as to what the ‘powder factory’ produced, talcum powder, face powder, perfume, flour, asbestos, dolomite, chalk or some sort of logging operation… even dynamite!

The “Powder” factory
Courtesy of the Dickson family

Having recently read our copy of Kaimai Revisited* we knew that the powder produced was actually eight different grades of diatomaceous silica, diatomite and pure silica from a nearby farm quarry. Diatoms are microscopic marine unicellular algae with cell walls composed of transparent, opaline silica. Over millennia these silica cases formed diatomaceous silica deposits on the ocean floor.

Silica Quarry 5 km up Ngamuwahine Rd
Courtesy of the Dickson Family

This silica deposit was discovered by Kaimai farmer Alex Dickson and a mining friend on his property Glenstrae in the late 1940s. In the early 1950s the company Glenstrae Products was formed. Shareholders included the Dickson family and local farmers Bill Scott and Ike Stephens. The raw product was dug and blasted from the huge hilly deposit some five kilometres up the Ngamuwahine Road at the rear of the Dickson farm.

Alex Dickson carrying a bag of silica
Courtesy of the Dickson family

It was crushed, partially dried in a nearby shed, trucked to the factory, where it was further crushed to a fine powder, then dried completely in a rotary kiln drier and bagged ready for distribution. When the factory was working, large clouds of white dust could be seen coming from the place, hence the ‘powder factory’. Later extractor fans with ‘wind socks’ were installed to reduce the dust.

Swift powder, as sold in shops (top) and sample boxes given out at the factory (bottom)
Courtesy of the Green family

The product was used in various ways - mainly as an additive to strengthen the concrete for the Atiamuri Dam on the Waikato River. A household cleaning product “Swift” was sold to shops. Other uses for diatomite included the addition to special insulating and refractory bricks, filters, roofing tiles and ceramics.

By 1960 the factory was no longer in operation and weeds began to take over the buildings. There were various reasons for the cessation of operations, one being a very wet season which created difficulty in drying and transporting the mined silica.

Glenstrae Farm (875 acres) was sold by the Dicksons to Max Brown in 1965. Two Nissen huts were moved to the 17th Avenue Historic Village in the 1970s, but not until 1979 was the company eventually wound up.

The factory being demolished
Published in Bay of Plenty Times, 10 July 1972
Collection of Tauranga City Libraries, Pae Korokī Ref. gca-20654

I have been told that during the 1970s there was a person making surf boards in one of the buildings, possibly the former office which is the relic that still may be glimpsed. There may have also been a proposal to reopen the quarry in the 70s or 80s but this did not eventuate. There is still a very large deposit on the farm as the estimation from test drilling, done at the outset, was that there were several million tonnes of various grades.

The factory being demolished
Published in Bay of Plenty Times, 10 July 1972
Collection of Tauranga City Libraries, Pae Korokī Ref. gca-20655

Our thanks for help with this article go to John Coster, and the three children of Alex Dickson — Peter Dickson, Janeann Freeman and Joy Holley. 

*Kaimai Revisited — 75th Jubilee of Kaimai School, edited by Betty Coubrough, publ. 1988