Story: Rock and mineral names
Observant naturalists and geologists exploring New Zealand have identified a number of unique or unusual rocks and minerals, often naming them after the place where they were found. Minerals such as taranakite have since been identified in other countries. Distinctive green-grey goodletite (named after its discoverer, William Goodlet), and purple tuhualite (named after Tuhua or Mayor Island) are found nowhere else.
Full story by Simon Nathan
Main image: Tuhualite crystal
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What’s the difference between a mineral and a rock?
A mineral is a solid substance with a definite chemical structure – for example, salt or quartz. All rocks are made of two or more minerals.
Common New Zealand rock names
Most of New Zealand’s rocks and minerals are found elsewhere in the world, and have names that are used internationally. The most common rock in New Zealand is greywacke (pronounced greywacky), and it is found on the mountains, in the rivers and on the beaches. If you find a grey rock, you will probably be right if you call it greywacke.
New Zealanders have their own names for some rocks:
- Papa – a Māori word for a soft, blue-grey mudstone that is almost like clay. Many cliffs are made of it.
- Pounamu – the Māori word for jade, or greenstone. It is used for jewellery and for carving. In New Zealand, pounamu is found only in the South Island.
Rocks first named in New Zealand
These are some rocks first discovered in New Zealand. Later their names were used for the same rocks in other countries.
- Dunite. An Austrian explorer, Ferdinand Hochstetter, noticed this rock on mountains near Nelson. When broken it is yellow-green, but the surface is rusty brown (dun coloured). Dun Mountain is where it was found.
- Ignimbrite. Rocks common in the central North Island are made of ash and pumice, thrown out from volcanoes. In 1932 they were named ignimbrite, from Latin words meaning ‘shower of fire’.
- Goodletite. Prospectors showed boulders of this rare rock, only found near Hokitika, to William Goodlet, and it was later named after him. It contains ruby and sapphire, and is prized by collectors.
Some minerals were originally found and named in New Zealand. They are usually named after the places where they were discovered.
- Taranakite. This is a fine-grained, cream mineral found in volcanic rock near New Plymouth, in the Taranaki region. It forms by a chemical reaction between bird droppings and weathered volcanic rock.
- Wairauite. This was found in the Wairau Valley, at the top of the South Island. It consists of tiny grains. Scientists need an electron microprobe to identify it.