Two fir cone halves of one whole specimen fir cone, now cut open and polished which enables an excellent study of the internal structure of the cone. Clearly the ovulate female cone displays seeds which would have eventually been pollenated by the male cones pollen. Male cones are much less spherical and do not hold seeds and are not as woody in appearance as the female cones. In the female cone here one can clearly see the ovules or seeds. The ovules become seeds once fertilised.
The ovules or seeds well defined in darker and lighter colours of fossilised silica or quartz, the surrounding borders of scales now solid limestone. The seeds are encased within the scales, until ripened, at which point the cone would have started to break up and fall apart, thus scattering the seeds, this has not taken place here. The scales are a coloured mineral of light beige. The central part of the polished cone has subtle rose to pink colours. The mineral iron in the sediments denotes the colours of the red scale and uranium yellow, greens and brown, silicom dioxide often creates greys and whites. The colour tones in this cone as mentioned above lead from subtle tones of pinks and beige, also coming through the mineral inclusions are greens, greys and in small amounts black, black is bedfellows with carbons.
In the specimen fir cone illustrated above, the minerals that were in heavy concentrations in the sediments at the time the cone was laid down, have per-mineralised with the rotting tissues, this vascular penetration in a cell by cell mineral metamorphism creating a solid quartz filled strobilus, strobili is an organic sporangia bearing structure, an enclosed structure where spores may be formed within.
Petrification involves replacement of the tissue within the fir cone, replaced by silica or calcium carbonate, the crystallisation of silica is a combination of pressure and heat. In this instance helping the fossilisation process and enabling us to view both ancient and modern fir cones in a comparison, reflecting the transition of a modern fir cone of today against the fossil cone.
It is often impossible to attribute silicified or similarly preserved woods to particular plants or trees. Usually a softwood which explains the attractive colours these fossilised fir cones produce from the Araucaria family, more commonly perhaps the Ginkgo’s or Monkey Puzzle tree’s.
An interesting footnote, modern day araucaria cones once pollenated take up to eighteen months to produce seeds to maturity this is when they start to fall apart.