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August 10, 2026
Still rolling out some fantastic specimens that we acquired this summer via private collections, public sales, and the two Oregon shows. Thanks for your patronage Beth and Jim ------ Friends of Fossil Forests Jim's presentation on 7/14 about Clover Creek Oak was very well-received. It is our understanding that it will be available for viewing on YouTube for members of the Friends of Fossil Forests. Just one more good reason to join, which you can do at this link: |
Welcome to Mills Geological quality identified petrified wood and plant fossils from around the globe |
Our Featured Specimen
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Tropical hardwood with Teredo borings (Dipterocarpaceae Family) Tertiary Indonesia ** Wow! There is always something new under the sun! At least, this was a new find for us since we had never seen Teredo Wood from Indonesia in the several decades that it has been available on the American market. This one is pure aesthetics. We've placed the specimen in the taxon Dipterocarpaceae Family but to be truthful, there is not much you can do with that information since there are nearly 700 living species spread across 22 genera in that family today. It is exclusively a "tropical evergreen hardwood" but not enough has been done with taxonomy of Indonesian fossil woods to be able to place a definitive tag on this interesting piece. We have included a photomicrograph of the structure - vessels in the range of 100 microns diameter, relatively low vessel density (perhaps a clue to the taxon of this piece since the majority of modern genera have much higher density). However most of the genera in the Dipterocarpaceae have wide variations in both vessel diameter and vessel density so even that fact may lead nowhere. So, we are going to emphasize the aesthetics of the piece. We have also included a closeup of one of the chalcedony filled tunnels. The polished face has excellent color; at least half of the borings are hollow with the classic mollusk calcareous lining (now pseudomorphed to chalcedony) and, there is an excellent view of the longitudinal axis of the tunnels on this end cut specimen's exterior and, don't forget that Indonesia is a unique (we think) place to find fossilized Teredo wood. Teredos are commonly called “shipworms," but, in fact, these boring critters are not worms at all - they are mollusks classed as Pelecypods. The paired shells of these bivalves have been reduced through evolution to two curved plates that lie alongside the animal's head, and the shell surface is equipped with serrations that can rasp on the wet wood and enable the animal to gnaw its way through the wood. The creatures have an uncanny ability to gnaw away at the wood without generally gnawing their way into a neighbor's track. The teredo creatures leave behind calcareous lined tunnels which are sometimes backfilled with mud and then hardened into mudstone and sometimes left empty. 5.5" x 3" on polished face" chunk of a trunk section up to 2.75" long $129 |
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Ancient conifer (Araucariaceae Family)
Chinle Formation, Sonsela Member, Triassic Twenty-two Draw, New Mexico ** Very attractive and colorful slab in shades of the color of fresh salmon from the border area of Arizona and New Mexico. The Sonsela Member is stratigraphically in between the Blue Mesa Member and the Petrified Forest Member of the Chinle Formation. The three members all produced petrified wood but they each have their own distinctive appearance and this specimen is typical of the Sonsela material that we see in collections. The Chinle paleoclimate was subtropical and trees grew continuously so they tend to lack any growth rings and end up looking quite tropical. The reason of course is that Arizona was centered at around 10 degrees north latitude during the Early Triassic and that placed it in climates similar to that experienced in modern time in Panama and Nicaragua which are definitely in the "tropics." We love these specimens that tell a story of their lives … AND that are so colorfully beautiful! 5" x 4" on polished face, 7/16" thick slab $49 |
Pepper (Schinoxylon actinoporosum)
Laney Shale Member, Green River Formation, Eocene
Blue Forest, Wyoming
** So, it is possible that you now have a pepper tree specimen from the Blue Forest, but like lifetime accomplishments, there is always room for one more of them! This slice has outstanding attributes! Some small cavities in the wood are filled in with gorgeous fortification agate. This piece also has numerous borer tunnels that are backfilled with insect frass. These are always an interesting conversation-starter. Additionally, this nice slice of “pepper tree” also has a great center. And … aesthetics are an important feature of this smaller specimen - we simply love the pattern created by the chocolate brown and black with the contrasting blue agate.
If you are interested in the taphonomy and mineralogy of petrified woods from Eden Valley, you can check out the lengthy article in the publication Geosciences that I coauthored in 2019 with George Mustoe and Mike Viney entitled “Mineralogy of Eocene Fossil Wood from the Blue Forest Locality, Southwestern Wyoming, United States.” It is open access and can be downloaded at https://www.mdpi.com/2076-3263/9/1/35 The article can explain, in detail, the complex process that resulted in specimens like this one.
3.75” x 2.5" on polished face; 3/16" thick slab $49
Laney Shale Member, Green River Formation, Eocene
Blue Forest, Wyoming
** So, it is possible that you now have a pepper tree specimen from the Blue Forest, but like lifetime accomplishments, there is always room for one more of them! This slice has outstanding attributes! Some small cavities in the wood are filled in with gorgeous fortification agate. This piece also has numerous borer tunnels that are backfilled with insect frass. These are always an interesting conversation-starter. Additionally, this nice slice of “pepper tree” also has a great center. And … aesthetics are an important feature of this smaller specimen - we simply love the pattern created by the chocolate brown and black with the contrasting blue agate.
If you are interested in the taphonomy and mineralogy of petrified woods from Eden Valley, you can check out the lengthy article in the publication Geosciences that I coauthored in 2019 with George Mustoe and Mike Viney entitled “Mineralogy of Eocene Fossil Wood from the Blue Forest Locality, Southwestern Wyoming, United States.” It is open access and can be downloaded at https://www.mdpi.com/2076-3263/9/1/35 The article can explain, in detail, the complex process that resulted in specimens like this one.
3.75” x 2.5" on polished face; 3/16" thick slab $49
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Maple (Acer sp.)
Laney Shale Member, Green River Formation, Eocene
Blue Forest, Wyoming
** A really attractive specimen with a nice pattern created by lenticular cavities filled with blue agate. The wood itself must have undergone tremendous tectonic pressures prior to petrification. The squiggly lines of medullary rays suggest that the once ramrod-straight rays and vessel pattern was changed forever by enormous pressures on the limb - likely when it was in a very wet and perhaps even spongy soft condition. That would imply a very thick and heavy downfall of volcanic ash squeezing the limb into seemingly impossible patterns. The vessels of this maple are at the upper end of sizes normally associated with the genus (around 90 microns). But, anatomy aside, what we really like is the pattern - perfect for any display shelf and cut as a standup specimen so that it does not need any additional holder to be perfectly displayed. If you are interested in the taphonomy and mineralogy of petrified woods from Eden Valley, you can check out the lengthy article in the publication Geosciences that I coauthored in 2019 with George Mustoe and Mike Viney entitled “Mineralogy of Eocene Fossil Wood from the Blue Forest Locality, Southwestern Wyoming, United States.” It is open access and can be downloaded at https://www.mdpi.com/2076-3263/9/1/35 The article can explain, in detail, the complex process that resulted in specimens like this one.
2.25" x 2" on polished face, standup that varies from 1.25" to 2.5" $45
Laney Shale Member, Green River Formation, Eocene
Blue Forest, Wyoming
** A really attractive specimen with a nice pattern created by lenticular cavities filled with blue agate. The wood itself must have undergone tremendous tectonic pressures prior to petrification. The squiggly lines of medullary rays suggest that the once ramrod-straight rays and vessel pattern was changed forever by enormous pressures on the limb - likely when it was in a very wet and perhaps even spongy soft condition. That would imply a very thick and heavy downfall of volcanic ash squeezing the limb into seemingly impossible patterns. The vessels of this maple are at the upper end of sizes normally associated with the genus (around 90 microns). But, anatomy aside, what we really like is the pattern - perfect for any display shelf and cut as a standup specimen so that it does not need any additional holder to be perfectly displayed. If you are interested in the taphonomy and mineralogy of petrified woods from Eden Valley, you can check out the lengthy article in the publication Geosciences that I coauthored in 2019 with George Mustoe and Mike Viney entitled “Mineralogy of Eocene Fossil Wood from the Blue Forest Locality, Southwestern Wyoming, United States.” It is open access and can be downloaded at https://www.mdpi.com/2076-3263/9/1/35 The article can explain, in detail, the complex process that resulted in specimens like this one.
2.25" x 2" on polished face, standup that varies from 1.25" to 2.5" $45
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Various names in commercial lumber (Sideroxylon sp.)
Little Butte Formation, Mehama Volcanics unit, Oligocene Ames Creek area, Sweet Home Petrified Forest, Linn County, Oregon ** The Genus Sideroxylon is just one of almost innumerable taxons of really hard and strong woods called "ironwood" in the modern-day commercial lumber trade. We are not using that commercial term because "ironwood" in rockhound parlance refers to petrified wood from the Palm Spring Formation found on the terraces on both sides of the Colorado River in far southern California and Arizona. There is an interesting story behind this identification. In her seminal article about petrified woods in Oregon, Irene Gregory listed Reptonia as one of about 50 genera she had identified. If you are not familiar with Irene Gregory, she was a professional paleobotanist and she formed the Beaver Hood Company in the 1970s specifically to sell identified petrified wood specimens. For years, I wondered why Reptonia was not included on the Insidewood website - eventually learning that it is a botanical synonym for Sideroxylon and also for Bumelia. Both of these genera do get hits on Insidewood, and I think the closest match to this specimen is Sideroxylon obovatum (https://insidewood.lib.ncsu.edu/description?59) which is now a South American species. While the modern South American wood seems to have more parenchyma than this Sweet Home specimen, it is otherwise quite similar. There are also several other species of Sideroxylon which are now found in Mexico and Central American, but unfortunately many of these do not have any photomicrographs on the Insidewood site to accompany their descriptions. But remember that the international rules of paleobotany require that in order to assign a fossil wood to a living species, one must have a matching reproductive structure ATTACHED to the wood since all living species are identified by their reproductive structure, not by their wood anatomy. Since we don't have an attached reproductive structure, this slab would be properly designated Sideroxylon sp. Note in the photomicrograph that the vessels are exceptionally tiny and occur in long sinuous swarms without any interruption by annual growth rings (which are very difficult to see but they can be seen as a faint seasonal line on the photomicrograph) and without obvious medullary rays. It's hard to know if this is a rare taxon at Sweet Home or not since I went several years not knowing what it looked like. But I can say that I only recently began seeing and identifying some of it after learning that Reptonia in Irene Gregory's published list of species is a botanical synonym for Sideroxylon and is now listed as such on Insidewood. In the past I would simply have called it an odd dicot wood ... 2.25" x 1.5" on the polished face; limb section 3" long $55 |
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Pepper tree (Schinoxylon actinoporosum)
Laney Shale Member, Green River Formation, Eocene Blue Forest, Wyoming ** Don't you just love the blue and gray botryoidal agate along the entire length of this limb section? Yes, that is a perfect description of this amazing piece. To make for a perfect display our lapidary cut off a bit of the end and then polished both of the cut faces - limb and end cut. That way it can be displayed numerous ways with always the possibility of showing the cut and polished face. The blue agate is simply among the best we have seen for quite some time and it complements the brown wood perfectly. It takes several photos to show just how covered over with blue agate this beauty is so if you are inclined towards aesthetic specimens, this one is for you; you have found a fantastic new specimen to add to your collection. 2” diameter on each cut and polished face, 3.25" in length limb section, .75" end cut $240 (and therefore immediately qualifies for our 10% discount on order totaling $200 or more) |