Dellen Tagamite Sweden

Dellen Crater is a roundish lake system in central Sweden near the east coast 180 miles north of Stockholm. It is about 11 miles across. The impact that formed it occurred 89.0 ± 2.7 million years ago.

Some of the impact rock from the site is called tagamite. It is a term that was introduced in 1975 to describe impact rock from the Popigai crater in Russia. Varieties of tagamites are described based on crystallinity, texture and clast content.

Some writers call these rocks by the local name “dellenites”. Others make the case for referring to all such as simply “impact melt rock”.

Eight millimeter wide view of a thin section of Dellen Sweden tagamite in transmitted light.

Brown impact melt glass containing crystals and mineral grains. FOV = 3mm. Dellen tagamite, Sweden.

The circular features are concentric curved fractures, “perlitic” texture. Dellen tagamite, Sweden.

Near the center of this view are several small dark fans of fine crystals in the solidified melt. FOV = 3mm. Dellen tagamite, Sweden.

In cross polarized light the glass is black. FOV = 3mm. Dellen tagamite, Sweden.

The dark fans are fine crystals that grew in the melt before it solidified. FOV = 0.3mm. Dellen tagamite, Sweden.

Another set of fine radiating crystals in the solidified impact glass. When Dellen material has this fine texture throughout it is called cryptocrystalline tagamite. FOV = 0.3mm. Dellen tagamite, Sweden.

Crystals and mineral grains in impact glass. Cross polarized light. FOV = 3mm. Dellen tagamite, Sweden.

Fractured mineral grain in impact glass. Cross polarized light. FOV = 0.3mm. Dellen tagamite, Sweden.

Mineral grains and inclusions in impact glass. Thin section in transmitted light. FOV = 0.3mm. Dellen tagamite, Sweden.

John Kashuba

John is a natural history enthusiast living in Oregon.