last update   3/21/17

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Mills Geological

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

Our Featured Specimen

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.. and thank you so much for your friendship and business.  

Beth and Jim

Palm fiber with roots Palmoxylon & Rhizopalmoxylon



** To our way of thinking, the very best palm slabs have some indication of roots on the periphery.  That philosophy often means having to get one in a larger size, maybe even in a wall-sized slab.  This is a medium-sized, very special example of Indonesian palm with well-preserved rootlets.  Since palms send out adventitious roots as they grow taller, the presence of roots on the periphery indicates that the slab is indeed a perfectly complete round and it was cut from a trunk location fairly close to ground level.  This one is a spectacular piece with not only the rootlets on the edges, but a great pattern in the center. The blue agate is actually filling in cavities produced by heart rot fungus. Palms (and other monocots) are particularly susceptible to heart rot because they don’t have the capability of producing toxins to protect themselves (for example, like terpenes in conifers which are mobilized in the medullary rays).  

Check out the nice preservation of the roots in our close-up photos to the right.  Terrific specimen!

12” x 10” on the polished face; 5/8” thick slab    $290

Note: This specimen immediately qualifies for our discount of 10% on orders over $200, and layaways are accepted!

Tucson Show 2017

Limb cast (Incertae sedis)

Tropico Group, Miocene

Boron Dry Lake near Mojave, California

** This limb cast could fool you – it looks like it has good preservation of the medullary rays but indeed there is inadequate preservation of the woody fine structure to determine any taxonomic affinity.  That does not limit the desirability of this piece!   The color and pattern are simply superb, and the fact that it was wood is not in dispute.  The proximity of Boron Dry Lake to Los Angeles -- and the top quality of the agate here -- caused this area to be totally collected out by the early 1970s.  Much of the material went for costume jewelry, not collector specimens, and this piece is a prime of example of why.  For the agate collector in you, this is one you will want to have for its beauty, its locality, and its agatized charm.   We are seeing less and less Boron on the market, so don’t let this one pass you by.  

2" x 2.25" on polished face; end cut varying up to 1" thick   $39

Conifer Limb (Natural and unpolished)

Trout Creek formation    Miocene

** There is just no other word to describe this 2.5” long limb section other than “charming.”  Fantastic exterior morphology, complete with knot, superb definition of rings, and some pretty autumnal color – all in one neat little package.  The opalized nature of the face of this wood makes it appear that it has been polished but, surprisingly, it has not!  This is the limb that we all hope to find on the ground in its natural state, but it would be a rare occurrence indeed.  

1” diameter on the unpolished face; 2.5” long limb section   $19

Haw (Viburnum sp.)

Late Oligocene to Early Miocene, Mehama Volcanics in the Little Butte Formation

Sweet Home area, Willamette Valley, Oregon

** Beautiful slab - with bark that is preserved on approximately half of its circumference.  We don’t see a lot of Sweet Home wood with bark, but in this slab the bark is either “frozen” in or on the edge of that band of white agate on the periphery.  Since bark (phloem) is more porous than wood (xylem), it tends to swell up faster with water than the wood (think of cork which is made from the bark of oak trees).  This log was underwater so that the bark actually pulled away from the wood when the pond in which it was waterlogged was covered by volcanic ash to begin the petrifaction process.  The space between the bark and wood was later filled in with the first precipitation of chalcedony from percolating groundwater.  The vascular structure of the wood is well preserved in several small portions of the slab.  Vessels are quite small (under 50 microns), evenly distributed throughout the growth ring and exclusively solitary.  Like the modern North America species of Haw, the rays are nearly invisible – tending to be only a single cell wide.  (See photomicrograph right.)  Modern species of European Haw tend to have somewhat wider rays than their North American cousins.

4.5” x 4” on polished face; 5/16” thick slab   $45

Unidentified species (Incertae sedis)

Golden Valley Formation Eocene

Cedar Canyon, near Medora, North Dakota

** This specimen, which comes from river gravels on private ranchlands near Cedar Canyon in the far western edge of North Dakota comes from the same Eocene Golden Valley Formation that outcrops with fossil wood in the nearby Theodore Roosevelt National Park, where the fossil forest is preserved for future generations.  It is a good example of a locality where small rounds are very scarce and the more common large rounds tend to be measured in feet, not inches. Indeed, you can find quite a few really large chunks of petrified wood from North Dakota on the market - it is mostly being sold as landscape material and likely is not anything near a complete round with a center pith. So we were quite pleased to obtain material that is appropriately-sized for display cabinets and drawers. The limb was dramatically attacked by fungal activity prior to petrification so we are unable to obtain a diagnosis of species of plant Family affiliation.  Nevertheless, it is a really attractive slice for the collector who favors aesthetics over all else!

3.5" x 2.5" on the polished face; 1/2" thick slab  $45