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March 12, 2026
Some great new specimens today! Thanks for your continued loyalty. Jim Mills and Beth Myers ------ Have you joined? The Friends of Fossil Forests is a group which encourages research and conservation, and connects professionals and amateurs interested in petrified forests. |
Welcome to Mills Geological quality identified petrified wood and plant fossils from around the globe |
Our Featured Specimen
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Primitive conifer (Araucarioxylon)
Chinle Formation, Triassic Tables of the Sun, San Juan County, Utah ** Much of the Utah petrified wood is black and we tend to avoid most of it simply on the basis of aesthetics. However, every once in a while, a piece comes along from a log that has terrific patterning -- and when we find those slabs, we jump on them and acquire them right away! This one is a fine example of the aesthetics that are possible when the dark black is also lightened with gray and tan to show contrasting areas of anatomy. It also brings up the question of annual growth rings; are those growth rings showing really explosive growth year after year? The Araucariaceae Family dominated the Mesozoic Forests. In the case of the Chinle Formation, the forest was located in the subtropical latitudes with a mild climate and year-round precipitation. That's why you see so few specimens with annual growth rings and some specimens with drought rings like these. Like the tropical and subtropical species today, those giant trees just kept growing and did not stop to rest (and thereby develop a growth ring) until their climate was subjected to a drought. Then, growth slowed down for a season or two but soon responded with a continuation of consistent growth until the next drought - likely several years in the future. If the markings on this specimen were growth rings rather than drought rings, this tree would have been only nine or ten years old when the volcanic event buried it under falling ash. That would be record growth for today's Araucaria trees - even for those grown in the controlled climate of a greenhouse. In the 220 million years that have passed since this tree was alive and well, the entire North American continent, including all of the Chinle formation, has migrated well north through the process now known as plate tectonics. It is wonderful to have a good story to go along with an aesthetic specimen! 10.5" in diameter on polished face, 5/8” thick slab $250 (immediately qualifies for our discount of 10% on orders totaling $200 or more) |
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Sycamore (Platanus sp.)
Mehama Volcanics Unit, Little Butte Formation, Oligocene Holleywood Ranch, near Holley, Sweet Home area, Oregon ** Here’s a handsome slab with a quite special attribute. If you are familiar at all with our western Sycamore (Platanus racemosa) you know that the bark is very smooth and quite thin. We have several growing on our ranch and note that they seem to retain the thinness throughout their lifetime. Perhaps that is why we see so little of the Sweet Home fossil sycamore with encircling bark. And that is the thing that makes this slice exclusive - it has at least 75% of the circumference of bark well preserved. We think so much of this feature that we have included a photomicrograph of a small portion showing the sieve tubes that carried water and nutrients up the tree and sugars back down to the roots. The wood of sycamore at the bottom of our photomicrograph is distinguishable by the even distribution of medullary rays (generally 1 to 3 cells wide) and the diffuse (even distribution) of its quite small vessels between annual growth rings. Then comes some swollen empty space where xylem and phloem have separated and is now filled with white chalcedony. Next comes the cambial layer with numerous sieve tubes easily seen and finally the subsequent layers of phloem in which sieve tubes are no longer functioning and thus becoming much less visible. Sycamores love a riparian habitat access to continual water from streams and ponds means they tend to grow evenly year after year even when rainfall seems to vary. The riparian habitat seems to give them a constant supply of underground water even if surface water is diminished. This slab demonstrates this feature quite well with even growth year after year. It had a happy life until the volcanic event cut that life short and covered the landscape with downed trees all covered with ash to prevent oxygen loving organisms to begin their digestion and destruction of the wood. We have spelled Holleywood correctly. It is named and spelled this way because it is just outside the tiny, unincorporated hamlet of Holley, Oregon. In the really old, mid-20th century rockhounding days, it bore the name "Marker Ranch," and we still see some labels from old collections with this name applied to specimens. The Holleywood Ranch was featured on a television series called “Cash and Treasures” many years ago. The ranch has produced some really exceptional wood -- even by the very high Sweet Home Petrified Forest standards! This specimen is a fine example of that quality. 5.5" diameter on polished face; 1/4" thick slab $75 |
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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 fortification agate. Others have the yellow calcite filling several cavities - we don't see it very much but not because it is rare. Many diggers and cutters soak their logs in acid to remove the calcite in hopes of finding botryoidal blue chalcedony lining the cavity. It happens - but not nearly as often as the cutters would hope for. So, we are always pleased to find slabs with the yellow calcite still intact. Aesthetics are an important feature of this specimen - we simply love the kaleidoscope appearance of the major limb with triangular sectors drawing the eye to it. We would be remiss if we did not point out that the blue in this Blue Forest slice is really dark blue - more aesthetics on display. To our liking, the slab has just enough of the lighter tan-colored peripheral coating of Colonia sp. algae. It really does frame the entire slab and adds interest as well as display quality. All in all, if you are looking for a Blue Forest slab to make all your other Blue Forest specimens envious - you have just found it!
6.25” x 5” on polished face; 1/4” thick slab $79
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 fortification agate. Others have the yellow calcite filling several cavities - we don't see it very much but not because it is rare. Many diggers and cutters soak their logs in acid to remove the calcite in hopes of finding botryoidal blue chalcedony lining the cavity. It happens - but not nearly as often as the cutters would hope for. So, we are always pleased to find slabs with the yellow calcite still intact. Aesthetics are an important feature of this specimen - we simply love the kaleidoscope appearance of the major limb with triangular sectors drawing the eye to it. We would be remiss if we did not point out that the blue in this Blue Forest slice is really dark blue - more aesthetics on display. To our liking, the slab has just enough of the lighter tan-colored peripheral coating of Colonia sp. algae. It really does frame the entire slab and adds interest as well as display quality. All in all, if you are looking for a Blue Forest slab to make all your other Blue Forest specimens envious - you have just found it!
6.25” x 5” on polished face; 1/4” thick slab $79
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Opalized wood - Poplar (Populus sp.)
Truckee Formation, Pliocene Sam Swartz Ranch, Hazen, Nevada ** An exceptionally outstanding limb cast with very nice preservation. The Sam Swartz Ranch at Hazen, midway between Fallon and Fernley in Nevada was a popular fee area for rockhounds. There were digs on both sides of U.S. Highway 50 on his ranch lands and he was mentioned in magazine articles as an affable host to rockhounds. Much of the opalized wood recovered from his ranch had distinguishing features of a light tan to rust color and highly opalized permineralization - a perfect description of this specimen. After Sam passed away, the ranch was sold and all rockhounding came to an abrupt end. It never restarted - but the specimens recovered during his lifetime now residing in older collections are being redistributed to a new generation of collectors – which is how it should be. A lot (and we mean a LOT) of the opalized wood went into costume jewelry since it possessed that particular glassiness typical of common opal which takes such a good polish. Here's an opportunity to carry on the tradition started by Sam by adding a fine limb of poplar to you own collection. 2.25" in diameter on polished face; 3.75" long limb section $59 |
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Conifer encased in algae (Pinales Order)
Miocene, Trout Creek Formation
Diggings near McDermitt, Nevada/Oregon border
** McDermitt has produced fossil wood in algae from three different sites where the specimens have been preserved in three distinct colors - a different color of the fossil algae at each site. We suspect the differences are the result of different volcanic events over the span of Trout Creek time. All of the geological evidence points to there being numerous eruptions separated by longer periods of quiescence in between eruptions. Color differences are most likely caused by complex differences of the geochemistry of the ash along with different chemical characteristics of the groundwater which began to weather the volcanic ash to provide the silica for permineralization. The result - brown, yellow and green coloration in the fossil algae. This specimen is from the yellow algae site. Hydrolization by the water has resulted in the disintegration of the wood tissue and much of the algal colonies as well. Fortunately, there is just enough remaining anatomy preserved to get a good identification on this particular stem to determine it was a conifer. The color changes between the three sites reflect the differences between iron oxides with different valences of the iron ion in the compound (yellow from limonite, brown from hematite and green from a trivalent iron compound. We love having all three sites represented in our own collection so they can be displayed beside one another to help illustrate the story of volcanic activity during Trout Creek time. We have reason to believe that all three sites are now completely depleted so this is a rare opportunity to add a yellow algae site slab to your collection if it is currently missing.
8” x 5” on polished face; 1/2" thick slab $65
Miocene, Trout Creek Formation
Diggings near McDermitt, Nevada/Oregon border
** McDermitt has produced fossil wood in algae from three different sites where the specimens have been preserved in three distinct colors - a different color of the fossil algae at each site. We suspect the differences are the result of different volcanic events over the span of Trout Creek time. All of the geological evidence points to there being numerous eruptions separated by longer periods of quiescence in between eruptions. Color differences are most likely caused by complex differences of the geochemistry of the ash along with different chemical characteristics of the groundwater which began to weather the volcanic ash to provide the silica for permineralization. The result - brown, yellow and green coloration in the fossil algae. This specimen is from the yellow algae site. Hydrolization by the water has resulted in the disintegration of the wood tissue and much of the algal colonies as well. Fortunately, there is just enough remaining anatomy preserved to get a good identification on this particular stem to determine it was a conifer. The color changes between the three sites reflect the differences between iron oxides with different valences of the iron ion in the compound (yellow from limonite, brown from hematite and green from a trivalent iron compound. We love having all three sites represented in our own collection so they can be displayed beside one another to help illustrate the story of volcanic activity during Trout Creek time. We have reason to believe that all three sites are now completely depleted so this is a rare opportunity to add a yellow algae site slab to your collection if it is currently missing.
8” x 5” on polished face; 1/2" thick slab $65
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Primitive conifer (Araucarioxylon)
Chinle Formation, Triassic
Circle Cliffs, County, Utah
** Terrific genuine old-timer here. We recently acquired specimens out of an old collection on which the collector had noted the exact location and year that the piece was collected. Circle Cliffs petrified wood is distinctive for the rich reds and rust-reds that contrast strongly with the blacks, browns and whites. That’s why we love this small slice - it has exceptional presence and is made-to-order for the collector with limited space to store and display their collection. (And maybe we all fall into that category …?) The Araucariaceae Family dominated the Mesozoic Forests.
In the case of the Chinle Formation, the forest was located in the subtropical latitudes with a mild climate and year-round precipitation. That is the reason you see so few specimens with annual growth rings. Like the tropical and subtropical species today, those giant trees just kept growing and did not stop to rest (and thereby develop a growth ring). In the 220 million years that have passed since this tree was alive and well, the entire North American continent, including all of the Chinle Formation, has migrated well north through the process now known as plate tectonics. If you value bulletproof provenance specimens coming out of old collections (like we do here at Mills Geological), this is a perfect fit for your collection.
2.75” x 1.75" on polished face; 1/4” thick slab $29
Chinle Formation, Triassic
Circle Cliffs, County, Utah
** Terrific genuine old-timer here. We recently acquired specimens out of an old collection on which the collector had noted the exact location and year that the piece was collected. Circle Cliffs petrified wood is distinctive for the rich reds and rust-reds that contrast strongly with the blacks, browns and whites. That’s why we love this small slice - it has exceptional presence and is made-to-order for the collector with limited space to store and display their collection. (And maybe we all fall into that category …?) The Araucariaceae Family dominated the Mesozoic Forests.
In the case of the Chinle Formation, the forest was located in the subtropical latitudes with a mild climate and year-round precipitation. That is the reason you see so few specimens with annual growth rings. Like the tropical and subtropical species today, those giant trees just kept growing and did not stop to rest (and thereby develop a growth ring). In the 220 million years that have passed since this tree was alive and well, the entire North American continent, including all of the Chinle Formation, has migrated well north through the process now known as plate tectonics. If you value bulletproof provenance specimens coming out of old collections (like we do here at Mills Geological), this is a perfect fit for your collection.
2.75” x 1.75" on polished face; 1/4” thick slab $29
Primitive conifer (Araucariaceae Family)
Chinle Formation, Triassic
Hite, Utah
** Way up north, just about as far north that the Chinle Formation can be found, Hite is located on Lake Powell in southern Utah and is surrounded by very rugged country. Remarkably, it is related to the same members found in Arizona - the Petrified Forest Member and the slightly younger Owl Rock Member. This one is a fine example of the aesthetics that are possible when the dark black has contrasting areas of gray. The Araucariaceae Family dominated the Mesozoic Forests. In the case of the Chinle Formation, the forest was located in the subtropical latitudes with a mild climate and year-round precipitation. That's why you see so few specimens with annual growth rings. Like the tropical and subtropical species today, those giant trees just kept growing and did not stop to rest (and thereby develop a growth ring). This specimen shows a few "growth hesitations" likely caused by temporary climate changes such as lack of adequate precipitation or unusually low temperatures. In the 220 million years that have passed since this tree was alive and well, the entire North American continent, including all of the Chinle Formation, has migrated well north through the process now known as plate tectonics. It is wonderful to have a good story to go along with such an aesthetic specimen!
5” x 2.75” on polished face, 3/8" thick slab $45
Chinle Formation, Triassic
Hite, Utah
** Way up north, just about as far north that the Chinle Formation can be found, Hite is located on Lake Powell in southern Utah and is surrounded by very rugged country. Remarkably, it is related to the same members found in Arizona - the Petrified Forest Member and the slightly younger Owl Rock Member. This one is a fine example of the aesthetics that are possible when the dark black has contrasting areas of gray. The Araucariaceae Family dominated the Mesozoic Forests. In the case of the Chinle Formation, the forest was located in the subtropical latitudes with a mild climate and year-round precipitation. That's why you see so few specimens with annual growth rings. Like the tropical and subtropical species today, those giant trees just kept growing and did not stop to rest (and thereby develop a growth ring). This specimen shows a few "growth hesitations" likely caused by temporary climate changes such as lack of adequate precipitation or unusually low temperatures. In the 220 million years that have passed since this tree was alive and well, the entire North American continent, including all of the Chinle Formation, has migrated well north through the process now known as plate tectonics. It is wonderful to have a good story to go along with such an aesthetic specimen!
5” x 2.75” on polished face, 3/8" thick slab $45