#ikaite

Glendonite star fossil

This fossil is not of an animal, but a mineral. When sea water temperature at the seafloor drops below ~4°C/39°F a carbonate mineral called ikaite will start to precipitate and grow forming bizarre shapes. Even though the original mineral will dissolve once it is buried, other diagenetic minerals will replace its form, making a glendonite.

Gledonite/Ikaite and its specific forming conditions allow geologist to approximate climatic conditions for the time period captured by the rocks in which this mineral is found.

Thanks to the flat exposure on the rock platform, we can appreciate this nature’s creativity.

Not a bone, not a dinosaur!

It is not a fossil bone, and it is not a dinosaur footprint either. This is a glendonite! It is a relic mineral that once grew at the bottom of the ocean which ended up being fossilized. When water at the bottom of the ocean or sea reaches near freezing temperatures, a particular type of carbonate mineral (type mineral that shells are made of) starts to form, usually taking shape of spires and pyramid-like forms which is called an Ikaite. It is a soft mineral and can break or dissolve easily, but if it ends up being buried, it can be fossilized to form the glendonite. This means that other minerals will replace it, while maintaining the original form of the mineral Ikaite.

Glendonites are used by geologists and palaeontologists to infer glacial conditions or near polar location at the time of sedimentation due to its exclusive formation at low temperatures.

Glendonite up close.

Close-up of the Permian glendonite fossil sticking out of the rock with much younger gastropod fossils on top of it.

and BIG glendonite deposit exposed on the rock platform in Australia.