Petrified wood is heavy because it is made of minerals that are much heavier than wood.
Let us explain.
Why is Petrified Wood So Heavy? (EXPLAINED)
What Is Petrified Wood, Exactly?
The heart to explaining this question is about what petrified wood is (and isn’t).
Petrified isn’t wood, not even close.
It is a mineral (like a rock).
Petrified wood started as wood, millions of years ago.
It got trapped somehow in an environment deprived of oxygen.
Under the water perhaps.
Under ash flows, or in a bog.
Since there is not oxygen, the tree couldn’t break down or decompose as it normally would.
The organisms that decompose the materials of the tree need oxygen to survive.
Over time (millions of years), groundwater flowing along underneath the surface of the lands flowed into the tree at a molecular level.
The cells in the tree slowly (very slowly) decomposed, and at different rates.
As areas decomposed, minerals dissolved in the water took the places of these molecular bits.
The process happened so slowly that the structure of the tree (down at the cellular level) remained intact.
This is why you can see rings in the specimen.
The entirety of the piece (including spaces in the material that would have held air), is made up of minerals.
Examples of minerals found in petrified wood include: silicon dioxide (which is also the base mineral for quartz, opal, and chalcedony), calcite, manganese, iron oxides, chromium, cobalt, and copper (among others).
Ok, Why Is Petrified Wood Heavy Then?
Petrified wood is much heavier than regular old wood, perhaps 2-3x heavier than wood, depending on the kind of wood.
The heaviness of either material has to do with the composition of the material (meaning what it is made of).
Secondary to that, is that the heaviness of the material is determined by how densely packed the molecules are that make up the material.
In materials that are densely packed (meaning molecules are close together), more molecules are found in a sample as compared to materials which are less dense (meaning fewer molecules in the same space).
When it comes to the materials that make up living wood, the molecules are less dense than the minerals that make up petrified wood.
The density of the molecules is why petrified wood is so heavy.
The density of the molecules is also why petrified wood doesn’t float (and living wood does).
Is Petrified Wood Heavier Than Rock?
Rock is a broad and vague term used to describe any number of materials that make up the surface of the earth.
As discussed above, the heaviness of a material is determined by the density of the components that it is made of.
Some rocks are lighter than others, given what they are made up.
Pumice, for example, is very light.
It is not dense at all, and even floats!
But it is still considered a rock as rocks are defined.
Thus, yes, petrified wood is heavier than some kinds or rock.
But it may also be lighter than others (peridotite and gabbro are pretty heavy).
Naturally, it also depends on the sample size.
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