Teredo wood is a fascinating specimen, especially for fossil collectors. These strange pieces of petrified wood are riddled with small spots, the remnants of ancient marine creatures. Left behind is a piece of ancient history, and something truly unique in the world of petrified wood.
So, let’s take a closer look at teredo wood, where it can be found, a
What is Teredo Wood?
Teredo wood is a petrified wood. Like most other fossils of this type, they’ve generally gone through some degree of silicification. This leaves behind a chalcedony “mold” of the wood that previously filled the space underground.
What makes teredo wood unique is the fact that it has “holes” across its surface. This gives the wood a Swiss-cheese-like appearance, although the holes have long been filled in as the fossil became mineralized.
In some cases, the holes aren’t filled all the way in. Instead, you’ll find them lined with crystals of quartz or calcium carbonate minerals that have formed a druzy on the interior of the calcareous tubes left behind by the ancient teredo species that ate into the wood.
Teredo petrified wood is most often seen as polished slabs, although it is occasionally cut into cabochons. This depends largely on the material’s origin, with the so-called “Peanut Wood” found in Australia being the most common in a finished form.
Teredo wood is actually the state fossil of North Dakota as well. It’s a common feature of the Cannonball Formation in that state.
What Caused the Holes in Teredo Wood?
The origin of the boreholes in this petrified wood is shipworms. These are actually a mollusk and have been known to cause issues since humans dropped their first wooden ship in marine waters.
These interesting little critters have a “shell” at one end. This shell is used as a makeshift drill, creating round holes in wood. They’re filter feeders, similar to other bivalve mollusks, and primarily eat macroalgae in addition to the wood they’re known for burrowing into.
They’re also extremely hardy. There have been no timber treatments found that will keep them away permanently. Indeed, the British Navy resorted to lining the bottom of their ships with copper plates to prevent their attacks.
They’re sometimes referred to as Sea Termites. It’s an apt name, considering the fact that they can destroy entire fallen trees in less than a year and they’ve been known to take down piers. They even caused the Dutch to have to revamp their dike system in the early 1700s before they brought them down.
They spend their lives as tunnelers. These tunnels are lined with a calcareous secretion, which is well preserved in toredo petrified wood. In addition, you can often find their shells in the petrified wood, where they resemble white crescents contained within the filled-in boreholes of the material.
What Kind of Fossil is Teredo Wood?
Fossil collectors should have a field day with this stuff. It’s actually a combination of a permineralization fossil (the petrified wood) and a trace fossil (the boreholes created by the teredo worms.)
Permineralized fossils are those that have had their tissues or other structures filled in entirely with minerals. Generally calcite or silica minerals. They’re what many people think of when they hear about fossils, with things ranging from dinosaur skeletons to petrified wood.
Trace fossils, on the other hand, are those that are known to have been created by biological activity in the past.
How Much Teredo Wood Worth?
A quick search shows that specimens of this type of petrified wood can be quite pricey. It depends a lot on the individual piece, but I was unable to find a slab of material for less than $40 and larger specimen pieces started at $90 and went up from there. The average was closer to $140 or so.
The specimen pieces tended to be complete rounds from 4” to 8” in diameter. Cabochons, when found, were likewise on the higher end of the scale for petrified wood.
Australian material with bright red and orange colors seemed to fetch the highest prices. It was also the only variety I found that seemed to lack actual holes entirely, which would make it suitable for lapidary purposes.
Where is Teredo Wood Found?
Teredo wood is found in a few different locations, and it seems to pop up at least occasionally anywhere that wood fell into marine water.
Perhaps the most famous formations of this material come from Australia. This is where the majority of the so-called “peanut wood” that can be found comes from. The wood from this area is generally completely mineralized and often lacks the holes left in samples from other locations. The tubes are generally a light color inside of a darker background.
In the United States, the most famous location is in Morton County in North Dakota. This is where the bulk of the Cannonball Formation can be found. Originally an inland sea, aptly called the Cannonball Sea, this area is known to house a ton of fossils dating back to the end of the Cretaceous. Teredo wood is a common find in this area.
This area also houses fossils of the other creatures that lived in the ancient sea. It appears that the dominant predators were sharks since the more well-known animals like plesiosaurs were extinct by that time.
The area around Kerrville, Texas also seems to house some of these fossils. They’re commonly sold online but I was unable to find an exact location. This wood tends to be light in color, with the boreholes showing up as white streaks. All of it that I located appeared to be some form of ancient juniper.
Actual holes lined with druzy quartz are also common in this material.
I also located a few bits that originated near Santa Barbara, California but I was unable to confirm exactly where they were pulled from. Santa Barbara Canyon is known to house petrified wood, so that would seem to be a safe bet.
Regardless, the conditions in all of these areas were the same: in the past they were warm, marine environments just like those the modern Teredo navalis prefers.