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September 27, 2026
We are on on our fall hiatus (which includes a visit to the Petrified Forest of Lesvos Greece and, by lucky timing, a visit to the Munich Show, Europe's largest gem and mineral show) so forgive us a late reply to your questions. We will be back in late October with some new specimens. So please come back! Thank you, as always! Beth and Jim ------ |
Welcome to Mills Geological quality identified petrified wood and plant fossils from around the globe |
Our Featured Specimen
Oak (Quercus sp.)
Sonoma Volcanics (Perlitic Rhyolite facies); Pliocene
Conn Creek Dam at Hennessy Lake, Napa County, California
** Out of an old collection comes this remarkable slab of oak discovered in the period 1946-1948 during construction of the Conn Creek Dam. In that era, earthen dams were often made by simply transporting material from adjacent canyons over to the new dam construction site and that is exactly how this log was discovered. The Sonoma Volcanics on both sides of the dam consist of both intrusive and extrusive rock that was mined and transported for the armoring of the dam after the clay interior core had been laid in place. It is indeed fortunate that rockhounds were on the site to identify and set aside a few logs, one of which produced this slab. Please note that the slab needed repair in two different places - lower right centered at the 4 o'clock position and lower left centered at the 8 o'clock position - so it was fortunate that the skilled lapidary did a very successful job of reattaching and obtaining a smooth surface front and back. If you are a California collector, this could be your one and only chance to obtain a specimen from this site. Special piece.
10" x 7" on polished face; slab 3/4" thick $125
Sonoma Volcanics (Perlitic Rhyolite facies); Pliocene
Conn Creek Dam at Hennessy Lake, Napa County, California
** Out of an old collection comes this remarkable slab of oak discovered in the period 1946-1948 during construction of the Conn Creek Dam. In that era, earthen dams were often made by simply transporting material from adjacent canyons over to the new dam construction site and that is exactly how this log was discovered. The Sonoma Volcanics on both sides of the dam consist of both intrusive and extrusive rock that was mined and transported for the armoring of the dam after the clay interior core had been laid in place. It is indeed fortunate that rockhounds were on the site to identify and set aside a few logs, one of which produced this slab. Please note that the slab needed repair in two different places - lower right centered at the 4 o'clock position and lower left centered at the 8 o'clock position - so it was fortunate that the skilled lapidary did a very successful job of reattaching and obtaining a smooth surface front and back. If you are a California collector, this could be your one and only chance to obtain a specimen from this site. Special piece.
10" x 7" on polished face; slab 3/4" thick $125
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Elm (Ulmus sp.)
Sedimentary Tuff; Upper Miocene Eagles Nest, Oregon ** An exquisite small but thick slab of elm from this classic locality. Eagles Nest is located south of the small community of Burns, Oregon and it has produced a wide variety of taxons over the years. This thick slice of a limb came out of an old collection dating from "olden times" when surface collecting was more successful than it is now at Eagles Nest. We particularly love the way the anatomy is preserved despite some obvious compression that took place prior to petrification. It is generally accepted that compression like this can result from being buried deeper in the volcanic ash that eventually provided the necessary silicon dioxide to complete the petrification process. The benefit of deep burial of course if that it definitely precludes oxygen that could allow for bacterial or fungal attack of the wood. Therefore the wood has plenty of time available to await the arrival of silica through groundwater percolation to begin filling any empty spaces in the xylem cells. So, even though not perfectly round as it was in its lifetime, it is perfectly preserved for all of geologic time. 2.25" x 1.75" on polished face; thick slice is 1" thick $37 |
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Cattail (Typha sp.)
Middle Miocene (Sarmatian strata, Tortonian age) Ratka, Zemplen Mountains, northeastern Hungary ** Well, this was a surprise. We acquired a flat of material in Tucson last year from Ratka, Hungary labeled "swampgrass" - a rather meaningless term used by dealers who are not well acquainted with paleobotany. It simply is an all-encompassing name for all of the vegetation that might grow in swampy or marshy habitats. We expected to find some of those Rhizocaulon huberi grasses for which the site is well known (and we did get some of them) but after cutting and sending several pieces to the lapidary for polishing we discovered that among all of the specimens there were some that were cattails. The surprise was doubly pleasing since we had only recently published a paper in Rocks and Minerals magazine on silicified cattails from Brown Butte, California. The diagnosis of cattail here relies on the morphologies of the pith (see our closeup of the polished end) and of the aerenchymous squared-off channels in the en-sheathing leaves (see our second closeup of the polished end). We are also attaching a photo of the unpolished end showing a longitudinal view of the ensheathing leaves. A perfect match of this unique arrangement. 1.5" x 1.25" on polished face; section is 3" in length $40 |
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Ancient extinct conifer (Woodworthia sp.)
Stormberg Group, Molteno Formation, Upper Triassic Gokwe Forest, Binga Territory, Midlands Province, Zimbabwe ** WAIT!! A Zimbabwe specimen but it is not green?? Well, there are plenty of Zimbabwe logs that do not have any green color and this specimen, pretty as it is, has a different story to tell. As you likely already know, the Triassic of Zimbabwe was quite tropical in climate meaning that annual growth rings are generally not seen on most of the petrified wood. BUT, take a look at our photomicrograph of one of the short shoot scars within the log and notice that there are clear annual markings all the way from the germination of this tree until its demise following a volcanic eruption. It makes perfect sense - the tree was growing continuously throughout the year at more or less a continuous rate from year to year without leaving any annual rings. But of course, the tree was simultaneously doing plenty of other activity at the same time. For example, the tree was producing pollen and cones only once per year and it was producing sugars in the foliage that were being transported down to the roots to store as starch. It thus follows that the short shoots, which have a limited period of growth each year would show a hesitation in growth every year as the seasons came and went. The very clearly defined traces of short shoot production that are seen on the polished face, makes this a terrific fossil find. These shoots were epicormic buds which the tree produced in the bark of the trunk have been described as a backup for preservation in case of a disaster that defoliated the existing foliage of the tree. If, for example, a wildfire destroyed the crown and its foliage of the tree, these buds would soon emerge to provide new leaves in order for the tree to carry on with life. The technical name of these epicormic buds in botany are preventitious shoots. A most interesting tree – one found in other Triassic strata on other continents as well. Gokwe is located in central Zimbabwe, and produced this wonderful specimen of Woodworthia. 8.5" x 8" on polished face; end cut varying up to 5/8" thick $59 |
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Conifer (Taxodiaceae Family)
Miocene (?) Mombacho Volcano, near Lago Nicaragua Masaya Department, Nicaragua ** While there is a considerable amount of fossil wood throughout Central America, we seldom see specimens on the market and that is doubly true for polished rounds with a center pith. That alone makes this a valuable addition to any serious collection of petrified wood. We are also impressed with the quality of preservation in this slab (see our photomicrograph) as compared to most of the other Central American petrified wood slabs we have seen over the years (admittedly the number of slabs is quite small). What little research has been published about the Miocene fossil woods of Nicaragua and Costa Rica has concentrated on the angiosperm taxons that might shine a light on the modern neotropical floras in this part of Central America. In our estimation that makes this Gymnosperm slab even more interesting - perhaps suggesting a higher elevation and poorer soil habitat for this slab compared to the researched Angiosperms. This slab is backed with fiberglass to add strength to the piece. 10" x 6.5" on polished face; 1/2" thick slab $150 |
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Ancient conifer (Gymnosperm)
Morrison Formation (Late Jurassic)
Hanksville area, Utah
** This log was well along towards becoming just vegetative debris on the forest floor when a volcanic event luckily saved it just in time for future petrified wood collectors. That history should tell you that the structure of this slab is not of the perfection that would send a paleobotanist right to the computer keyboard to write an article. Instead, it would be of more interest to those collectors who value the patterns created by bacterial and fungal activity after the tree is dead and down. Fortunately, those bacteria and fungus were stopped dead in their tracks just in the nick of time when buried by volcanic ash in the Late Jurassic. No oxygen meant no more destruction and soon, groundwater carrying silicic compounds along with traces of iron oxides began the process of permineralization. Those bands of fortification agate near the periphery are the result of desiccation and shrinkage cavities being the first areas to receive precipitation of silica - well prior to that silica also included mostly iron and manganese chromophores to darken the silicification of the wood. The luck of the lapidary even exposed a small cool spike knot coming out of the limb at the 2 o'clock position. This specimen came out of an old collection and the previous collector thoughtfully penned the place and date on the reverse side to give positive assurance of the provenance for this wonderful specimen. This one tells its own colorful petrification story and collecting history.
5" diameter on polished face; 3/4" thick end cut $65
Morrison Formation (Late Jurassic)
Hanksville area, Utah
** This log was well along towards becoming just vegetative debris on the forest floor when a volcanic event luckily saved it just in time for future petrified wood collectors. That history should tell you that the structure of this slab is not of the perfection that would send a paleobotanist right to the computer keyboard to write an article. Instead, it would be of more interest to those collectors who value the patterns created by bacterial and fungal activity after the tree is dead and down. Fortunately, those bacteria and fungus were stopped dead in their tracks just in the nick of time when buried by volcanic ash in the Late Jurassic. No oxygen meant no more destruction and soon, groundwater carrying silicic compounds along with traces of iron oxides began the process of permineralization. Those bands of fortification agate near the periphery are the result of desiccation and shrinkage cavities being the first areas to receive precipitation of silica - well prior to that silica also included mostly iron and manganese chromophores to darken the silicification of the wood. The luck of the lapidary even exposed a small cool spike knot coming out of the limb at the 2 o'clock position. This specimen came out of an old collection and the previous collector thoughtfully penned the place and date on the reverse side to give positive assurance of the provenance for this wonderful specimen. This one tells its own colorful petrification story and collecting history.
5" diameter on polished face; 3/4" thick end cut $65
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Large Pith Conifer (Dadoxylon sp.)
Mesozoic Madagascar ** A really unusual offering from Madagascar! If you are someone who has been looking at our website for several years you already know that it had been a "blue moon" since the last time we listed specimens from Madagascar. But we recently came across this really interesting Madagascar slab in an old collection. The market has been flooded with petrified wood from Madagascar for several decades and it would surprise us if there is anybody left out there that does not have the country very well represented in their collection. So, any slabs we list from Madagascar must be really special with colors and patterns that will appeal to our discerning Mills Geological collector friends. This one is a relatively scarce large pith (artisia) Dadoxylon. Indeed, this specimen is nearly entirely center pith - those "V" shaped structures are called the initial points where the primary xylem of the pith changes to the secondary xylem of the wood itself. While the practical result of a large pith makes any Dadoxylon a worthwhile addition to a petrified wood collection, this specimen has a pith "on steroids" (for lack of a better analogy)! Check out our photomicrograph. The large artisia measures approximately 2.25" x 2.0". Better yet is the fact that these initial points are individually colored a yellowish mustard hue that helps them stand out very clearly even without the aid of magnification. In most families of arborescent vegetation the pith artisia is quite small - sometimes so small that magnification is needed to see it. Compare the Madagascar pieces already in your own collection with this beauty and see if you are ready for a reasonable cost upgrade or an addition to that group. We promise you won't be disappointed with this specimen. 4.75" x 2.75" on the polished face; 1/4" thick slab $60 |
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