last update   9/17/17

Welcome to

Mills Geological

High-quality, identified petrified wood and plant fossils from around the globe

Our Featured Specimen

Our trip to Oregon was highly successful, so along with our other recent acquisitions, we have new wonderful specimens to offer!


Beth and Jim

Conifer (Pinales Order)

Columbia Plateau Basalt Group; Miocene

Vantage, Washington

** Aesthetics abound in this slab from the heralded collecting area of Vantage, Washington.  This slice offers very tight and well-defined growth rings.  Even the novice can recognize this slice as fossil wood.  Vantage is the little community right outside the Gingko Petrified Wood State Park.  This stunning slice comes from a ranch outside the park so it is a completely legal/legitimate specimen.

7.5” x 5.5” on polished face, 3/8” thick slab   $139

Juniper (Juniperus sp.)

Toe Jam Creek Formation, Oligocene

Tuscarora, Nevada

** A phenomenal slab from a renowned locality with a humorous formation name!  The Tuscarora locality is famed for its brilliant shades of red, orange, gold – and its interesting patterns.  This slab is from an old collection.  How do we know that?  No one we know today is cutting slabs from logs this gorgeous at 1/2” thick!  All of the wood we have ever seen from Tuscarora is "squished" (a not-so-technical term) indicating that perhaps it was quite wet and spongy when it was buried under a great deal of volcanic ash. It is possible that the deposit might have been a pond with sunken logs in a "waterlogged" condition, making them susceptible to being compressed by the great weight of the ash into oval and diamond shapes instead of their original round configuration.  Part of the story that goes with this fabulous wood!

12" x 6" on polished face; 1/2" thick slab   $195

Primitive conifer (Araucarioxylon)

Chinle Formation, Triassic

Southern 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 can be lightened to show contrasting areas of gray and tan. There are even some red and gold highlights in this specimen. But one of the most exciting features is that knot at the 6 o’clock position about 2/3 of the distance between the center and periphery of the specimen.  We only very seldom see knots in Chinle-aged logs.  Can’t say they are rare, but “scarce” would be an appropriate term.  Those are the reasons why we love this slab - it has an exceptional presence that will make your other southern Utah specimens envious if they have to share their space with it in your display case!


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.  It is wonderful to have a good story to go along with an aesthetic specimen!

9” x 7.5” on polished face, 5/8” thick slab   $179

Pepper tree (Schinoxylon actinoporosum)

Laney Shale Member, Green River Formation, Eocene

Blue Forest, Wyoming

** We try to avoid using the word “cute” when describing petrified wood specimens, but this great piece won’t settle for anything less than cute!  It is a relatively small stick of pepper tree, measuring just around a half inch in diameter, but it is perched just perfectly on the original matrix of fossilized Colonia sp. Algae.  It is a super display piece – one that even the most uninformed novice would immediately recognize as fossil wood.  The wood itself has nice exterior wood grain character and is partially covered with agate for about half of the distance. This piece is not cut and polished -- it is perfect in its natural condition!

Approximately 2.5” x 2” in cross section with 1/2”diameter stick;

overall length of specimen is 4.5”   $35

Ginkgo leaf    (Ginkgo adiantoides)

Sentinel Butte Formation, Paleocene

Almont, North Dakota

** A really outstanding specimen of this species from the locality that has produced some of the best Ginkgo leaves ever discovered.  Sadly, the site has a history that caused the ranch property owner to close it off to all collecting.  During the last half of the twentieth century. the site had been successfully collected by Princeton University paleontologists and museum professionals from the Field Museum in Chicago.  It was also open to individual collectors wanting to collect some of the many species found at the site.  But then, the calamity occurred.  Someone had brought explosives without permission and made a tremendous mess of the site.  The rancher was rightly outraged and cut off any future access by anyone but a very small cadre of personal friends.  This of course impacted the supply side of the classic supply/demand curve and prices have now reached levels once thought improbable.  We were able to acquire this specimen out of an old collection and we were glad to get a price comparably low when contrasted with the prices now charged for similar (and often lesser quality) specimens at Tucson each year.  The leaf is 2.75 inches wide across the bottom side where the petiole attaches.  There are even two additional large Ginkgo leaves on the reverse side of the plate but they are not complete as is the one on the side we photographed.

6.5” x 4.5” is the overall size of the plate; plate varies from .5” to 1.25” thick   $95

Bald Cypress (Taxodium sp.)

Columbia Basalts Group, Miocene

Saddle Mountain, Washington

** So just what makes this specimen unusual enough to qualify for our “featured” spot?  Saddle Mountain wood is almost always beautiful, and this one certainly  is.  The colors in Saddle Mountain wood are almost always “wood-like” and attractive.  Check.  But this piece has something that is rather special.  It has several different “centers” (five of them by our count) but only one of them was dominant.  This was likely a strong limb (not a trunk) which had four different side branches and twigs which never got past an early age before being completely encapsulated by more rapidly growing xylem of the main limb.  The largest branch only achieved eight years of growth while the smallest of the group only achieved five years.  These kinds of features contribute to outstanding patterning in slabs of petrified wood and make them excellent display pieces.  If you already have a slab of this great wood from this locality, it may be time to upgrade or add an additional specimen!  Nice manageable size, warm autumnal colors.


Bald cypress occurs mainly along riparian wetlands subject to periodic flooding by silt-rich "brownwater" rivers.  The generic name is derived from the Latin word "taxus" meaning "yew" and the Greek word "eidos" meaning "similar to."  The trees are especially prized for their heartwood because it is extremely rot and termite resistant.  The heartwood of living trees contains a sesquiterpene called cypressene, which acts as a natural preservative.

7.5” x 5.5” on the polished face;  7/16” thick slab   $129