Fossil diatom image


Behind the scenes. This is the first blog in a series of three focused on the North Otago Museum’s geology collection.

Behind the scenes we are doing a lot of work on our collections. This is to support the Cultural Facility Development Project. Recently Dr Margaret Bradshaw, a geologist, spent a day with me at the museum. Margaret was able to assist me in better cataloguing our accessioned geological collection. She also helped me begin reviewing some of the items that aren’t accessioned. This will help us decide which ones we should keep. I learnt a lot about our collection and about geology. One of the important things I learnt more about are diatoms.

What are diatoms?

Diatoms are a type of single celled algae. The diatoms in our samples are millions of years old but there are still diatoms alive today. A cell wall made of silica surrounds each diatom. This is called a frustule. Under a microscope the different shapes of the frustules are striking.

What is in the geology collection?

In the collection we have three samples of diatomite. Diatomite is a type of sedimentary rock largely comprising of the remains of diatoms. Diatomite is amazing stuff. It is super absorbent and it was used to make dynamite (and kitty litter!) We also have some microscope slides of diatoms.

What is the Waitaki connection?

Thomas Forrester (1838-1907) was the museum’s first curator and a keen amateur scientist. He had a passion for geology. In 1865 Thomas Forrester drew the first geological survey map of New Zealand for James Hector.

North Otago is world famous (if you're a diatomist) for its diatoms. So how were they discovered? This recollection of the discovery is by John, the son of Thomas Forrester.

“The discovery came about in a rather extraordinary way. I remember a day in 1886, when Dr. Von Haast, a name which will always be remembered in connection with the Canterbury Museum, called at the Museum looking for geological specimens characteristic of the district, for exhibition at the Indian and Colonial Exhibition held in London to mark the jubilee of Queen Victoria. Amongst other things he selected a lump of very light earth material labelled Kaolin (China Clay) and as kaolin it went to London. This lump of clay disappeared bit by bit, for various microscopists soon found it was diatomaceous earth of great interest. That bit of earth caused quite a furore in microscopical circles all over the world and soon letters were received here begging for pieces. The first letter came addressed to the person in Oamaru interested in science which the Postmaster (Mr J. A. Hutton) handed to my father knowing of his interest in geology. Later many letters came to my father with the result that pieces of the earth went to places widely spread over the world.”

The Oamaru Museum’s other curator, Dr de Lautour, also became interested in diatoms. Soon many locations containing deposits of diatomite were identified in North Otago .

Interest in North Otago’s diatoms continues. Later this year the Forrester Gallery will be exhibiting Beneath An Ancient Sea: Oamaru and the Glass Archive. This is a photographic exhibition by Wayne Barrar which explores diatoms. The photographs of the diatoms are stunning. Check out the Culture Waitaki website for more details.

Chloe Searle