Mineral description : Zircon

Zircon from Seiland, Norway.

A 2 cm zircon crystal in biotite, from Seiland, Norway.

Zircon and albite on orthoclase, from Langesundsfjorden, Norway.

Zircon in feldspar, from Langesundsfjorden, Norway.

Mineral class	Silicates : Nesosilicates : Zircon - tantalite group.
Chemical formula	Zr(SiO4)
Crystal system	Tetragonal
Habitus	Short prismatic dipyramidal crystals or irregular grains.
Cleavage	Imperfect, uneven to conchoidal fracture.
Hardness	7.5
Density	4.6-4.7
Color	Colorless, red, brown, yellow, green or gray. Transparent to opaque.
Streak
Luster	Vitreous, adamantine to greasy.
Description
Occurance	In granites, pegmatites and nefeline syenites.
Associates
Notes	Often radioactive due to small amounts of thorium and uranium. (Up to 14 %) Zircon is often metamict (no crystal structure) because of the radioactivity thats destroyed the internal structure. Zircon is a very good mineral to measure the age of rocks. It encapsules the uranium and the rest product, led, so it is possible to measure the age of different layers in a zircon crystal. The oldest zircon found in Sweden is 3300 million years old. Flourescent in UV-light.
Locations	A common mineral in microscopic amounts. Ytterby feldspar quarry, Stockholm. Finnbo and Kårarvet, Falun. Högsbo, Göteborg. Ås, Alnön. Penseryd and Stenberget, Romelåsen, Skåne. Storåsen, Medelpad. Seiland, Alta, Norway. Crystals up to 10 cm in biotite. Langesunsfjorden, Norway. Oslo, Norway. In holes in nordmarkite. Tördal, Norway. In cleavelandite with topas, beryll, lepidolite and cassiterite.

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