Opalization?

[TeaRex]

I was wondering a few things about opals effect on fossils and bones in general. 

1) does it degrade the value?

2) how long does it take?

3)how does it work?

4) would I be able to do it to some spare animal teeth? (Hope that’s not weird haha)

[DPS Ammonite]

Welcome to the Forum.

 

There are no exact answers for most of your questions but, I'll try.

 

1  I would think that a fossil replaced with pretty, common opal would increase the value. Fossils replaced with precious opal, such as the mosasaurs (EDIT: plesiosaurs instead of mosasaurs)

from Australia command a huge premium over both their fossil value and their precious opal value.

 

2  According to experiments in Japanese hot springs, they determined that wood could be fully silicified in a few decades. Wood buried in NW US volcanic deposits are mostly silicified after a few hundred thousand years. Most petrified wood on the surface is at least a couple or few million years old. So, the process can be quick or it can be slow.

 

3  Silica rich water fills in the spaces and silica is deposited in the wood as the wood slowly decays and shrinks. Burial under anarobic conditions is required.

 

4  I have never heard of anyone able to replace teeth with common opal. Even if you could, it would not be worth your time for what the tooth would sell for. However, if you could come up with a process to make high quality precious opal quickly you might be able to make a lot of money. 

[Fossildude19]

LINK

[The Amateur Paleontologist]

Welcome to The Fossil Forum, @TeaRex  

I'll try and answer your questions...

 

1) How to say - yes and no. Yes because in most cases, complete opalisation of fossil material leads to a loss of internal detail (crucial for biochemical, taphonomical etc. analysis). On the other hand, the value of the fossil is also increased - especially when the the fossil is replaced by precious opal, which is rather rare.

 

2) Duration of opalisation depends on various abiotic factors, such as concentration of silicon dioxide relative to water, rate of deposition/sedimentation… These factors imply that opalisation can last between a few thousand (some plant material) and a few million years (most animal fossils)

 

3) Imagine a shallow, silica-rich sea. When, let's say, a belemnite dies, it will leave only "leave behind" a hard rostrum (or 'guard'). That rostrum will be covered by sediment on the sea floor. Following that, it will be disintegrated (not sure how though.. I don't really know the chemical process)- thus allowing the silica-laden water to fill the mold left behind. After some time, the water will evaporate. What remains is a silica "gel" cast of the belemnite rostrum, which will eventually dry up and harden. 

 

4) I had not heard of that idea - but it sounds interesting.. I'm not sure how you could do it. You'd have to make a tooth-shaped imprint in some non-porous rock, and then fill that imprint with some sort of silica-rich water 

 

Hope this helped!

 

Christian

 

P.S. Just to let you know, @DPS Ammonite, the famous opalised marine reptile skeletons you were referring to aren't mosasaurs, but plesiosaurs. The age of those skeletons is of approx. 100-120 million years (Aptian-Albian), so quite some time before the first mosasaurs appeared