Originally published on Tumblr and FB in January of 2017
Q: What’s the difference between petrified and fossilized?
A: Petrifaction (petrification) is a PROCESS by which something becomes a fossil by way of either permineralization or replacement.
PETRIFY (verb): change (organic matter) into a stony concretion by encrusting or replacing its original substance with a calcareous, siliceous, or other mineral deposit.
FOSSIL (noun): the remains or impression of an organism from a past geological age that is preserved in petrified form or as a mold or cast in rock.
Types of Petrification: 1. Permineralization, and, 2. replacement.
In permineralization, the organism’s remains are saturated by mineral rich groundwater, which fills all of the microscopic pores and cavities. This forms stoney fossils that retain much of their original solid material.
Types of minerals in this ‘hard’ water include quartz, calcite, pyrite, hematite, siderite (iron carbonate), and apatite (calcium phosphate). How rich this groundwater is in minerals also dictates the structure of the petrified a-v-o fossilized material.
Replacement takes place when water dissolves the original hard parts and replaces them with mineral matter. This chemical action may take place slowly, reproducing the microscopic structures of the original organism. Bone, shells and wood are often well preserved in this manner. The most common replacement minerals are calcite, silica, pyrite and hematite.
The structure of the fossil is similar down to the microscopic level.
Petrified wood rates between 7 and 8 on the Moh’s Hardness Scale.
Petrified matter is different types of colors depending on the minerals involved: Iron will yield reds and yellows. Blues and greens will come from manganese and copper. Crystals like quartz will give the fossil a glittery appearance.
Have a great day! With love and in peace, Dawn
How do things become petrified or fossilized? Two conditions must be present. Firstly, an anaerobic environment (lacking oxygen that would lead to decay and decomposition.) This also means that it would have to be covered rather quickly, sometimes by mudslide or volcanic ash. Marine life is most commonly preserved, as are the remains of animals and plants that fell into low oxygen water to be covered by mud and silt. The second thing that would need to be present would be some hard part of the structure (jellyfish are rarely if ever found as fossils).
Other types of fossilization include:
– replacement – pyritization
– permineralization – mineralization, silicification
– ulaltered remains, having been frozen or covered in tar pits
– trace fossils, showing the activity of prehistoric life as opposed to the organism itself
In some cases, original material can still be present!
OTHER TERMS: ossified may be used, as it can mean fossilized or petrified. I would personally use it to mean “to turn into bone” or hard as bone, maybe like the cinnamon rolls I made in my twenties. Calcified is apt, since calcite is the main mineral that many fossils, especially ammonite, contain. I have heard a person refer to the yellow calcite in ammonite fossils as ‘amber’, but it is not amber. See tomorrow’s article!
QUESTION NOW: Do you like petrified wood or fossils, or both?
FURTHER READING: Search pyritized fossils, ice age mammoths and rhinocerous preserved by freezing, moulds and casts of prehistor living organisms, trace fossils…