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Story: Gemstones

Chert, flint and jasper

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Chert, flint and jasper are opaque forms of ultrafine-grained quartz. Jasper is distinctively red or multicoloured. Flint is a hard variety of chert, often found as nodules in limestone.

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Te Ara - The Encyclopedia of New Zealand

Photograph by Alastair McLean

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How to cite this page

Jocelyn Thornton, Gemstones – Quartz, Te Ara – the Encyclopedia of New Zealand, https://teara.govt.nz/en/interactive/5123/chert-flint-and-jasper (accessed 4 June 2026).

Story by Jocelyn Thornton, published 2 March 2009.

Comments

John Sherwin
21 December 2022
Quartz (SiO2 - silica) can be "massive" rose or white quartz reefs formed from molten magma. Or chemically "precipitated" as crystals from volcanically atomised silica out of ash dissolved water filling cracks or cavities. Silica chemically "precipitated" (crystalised) can be clear or coloured hexagonal form, formless (cryptocrystaline) tiny crystal mass of various colours or coloured and clear layers. Tiny marine skeletons of silica and limestone form layers of limestone OR flint and end up as layers in the ground sometimes associated with coal layers. Argilated (chalk) limestone can have pure translucent pockets of translucent flint nodules deal for stone tools. Flint formed in silt is notorious for having sand pockets and coarse areas referred to as "concrete". Course opaque silica with impurities is called chert.