An exceedingly well preserved fossil araucaria fir cone, illustrating how the female fir cone has mineralised with a wonderful array of naturally formed colours, which denote the surrounding fossil bed environment. Colours are an indicator as to which minerals were present in the fossil layer at the time of petrification and metamorphism of the fir cone. irons are represented by red tones, white or creams by silicium dioxides, greens for Uranium with blacks for carbon. Also in this marvellous image are clearly seen the seeds, which are the ovules the not yet mature seeds, these are the embryo, this elongated cut through section illustrates the ovules in the cone-scale, these cone scales held the DNA coding to grow a Araucaria mirabilis tree.
The fossil fir cone pictured forms part of our online collections for sale and are exceptionally well preserved, illustrating why these fossils are so popular with collectors and anyone interested in fossils and natural history. First we explain a short history of how the fossil fir cone is preserved. The fir cones originate from the Jurassic period and were found in old Patagonia, the supercontinent Pangea which formed part of Gondwana (around 300 million years ago), when the land masses of the world were one massive continent before the separation of tectonic plates in the Jurassic period around 175 million years ago, about the time Pangea separated from Gondwana. At that time great forests of Araucaria trees grew over 60 metres tall. In some cataclysmic event the trees were felled. Huge flood events carried trees some distance and deposited the de-branched trunks onto mineral rich sodden ground as the floods subsided.
Through a process of per-mineralisation the wood and cones were changed, at first by petrification and eventually fossilisation. The process of petrification in the case of wood and cones of this region was one of water heavily laden with minerals was forced through the rotting tissues, Micro crystalline quartz hydrates, this process is known as silicification, calcedony or opal could form, depending on the minerals deposited. Some agate, amethyst and citrine replacement also occurs, this is then psuedomorphosis. this process of silicification on a cell by cell and vascular level had the effect of eventually turning the tissue of the wood or fir cone to quartz, as the minerals hardened over time leaving the wondrous colours we see today.
We hope you enjoyed this short read on the process of making a fossil fir cone and will read more on our website catalogue, each fossil specimen fir cone is described and has snippets of different information to eek out for you budding naturalists…