MILLS GEOLOGICAL

Our featured specimen

Black Locust (Robinia sp.)
Trout Creek Formation, Miocene
McDermitt, Nevada/Oregon
** An outstanding slab of Black Locust (Robinia sp.) with excellent woody fine structure -- see photomicrograph. The McDermitt area has several diggings locations within a 15 to 20 mile radius. This piece from the Bretz Mine airport site is immediately obvious, even to a novice, that it is petrified wood. That's a good thing --- whether you exhibit your collection at shows or just in your living room! We generally identify the site as McDermitt, Nevada, which is both the closest inhabited place as well as the access point to the dirt roads leading to the diggings. However, the diggings are just across the border in Oregon (Malheur County), but it takes a GPS to find that out. There are no signs on the dirt roads announcing "Entering Oregon." This is an excellent slab from the area!
7" x 5.5" on polished face, 7/16" thick slab $70

Conifer (Pinales Order)
Toe Jam Creek Formation, Oligocene
Tuscarora, Nevada
** This piece is literally dripping with unusual colors! A gorgeous slab from a renowned locality -- with a humorous formation name! The Tuscarora locality is famed for its brilliant shades of swirling rust color patterns. The accenting blue and white portions add to the pizazz (and landscape quality) of this great specimen. 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! And it does nothing but accentuate the beauty here. Also please note the generous thickness at 3/4"
12" x 5.5" on polished face; 3/4" thick slab $129

Yew (Taxus sp.) in Stromatolitic Algae
"Tonopah Wood"
Miocene
Tonopah, Nevada
** An exceptionally beautiful example of “Tonopah Wood” with fabulous color and patterning of the algae! Old-timer rockhounds gave these attractive specimens the name "Tonopah" after the nearby old mining town of the same name in Nevada. The wood was under water and encased in stromatolitic algae prior to the volcanic event that filled the water body with ash and began the petrification process. The mineralization of the algae in this specimen has the very desirable salmon pink coloration. The wood itself is at the center of the slice. Much of it has been macerated and broken apart but enough anatomical structure remains to determine that it was a Yew (Taxus sp.). Maceration makes considerable sense because the wood must have been under water for quite some to enable the growing stromatolitic algae to completely encapsulate the wood. As a result, the specimens from Tonopah are generally valued more for their aesthetic appeal than for their wood anatomy. If you are also an algae enthusiast, the differentiation of mineralization (color) and form (some colonies small, some larger) make this an even more interesting specimen.
3.25" x 2.5" on polished face; 3/16" thick slab $40

Petrified wood (Incertae sedis)
Grassy Mountain Formation Early to Middle Pliocene
Grassy Mountain, Malheur County, near Vale, Oregon
** Beautiful agatized specimen from the noted Grassy Mountain locality, which has arguably produced some of the most colorful specimens in the entire world. Mustard yellow, deep bluish purple, lighter blue gray. Aesthetics are at the top of the list for this slab. Totally unfractured, growth rings suggested by alternating yellows and blues. We expect the material from Grassy Mountain to become very scarce in the not too distant future - gold mining is being planned and the area will become a giant open pit mine. Any petrified wood will be buried in spoil piles or be crushed along with the rest of the gold ore. A sad ending to a fantastic petrified wood locality. Grassy Mountain specimens should become very scarce in the market. This one is a knockout.
6.75” x 3.5" on polished face; very thin 3/16” in thickness slab $95

Limb cast (Incertae sedis)
Andesite and Basaltic overlapping flows Middle Miocene
Brogan, Oregon
** Incredible color with a really gnarly exterior. That pretty much sums up what we love to find in a limb cast and this specimen has it in "spades." The lovely light to dark purple color and the contrasting white rind make this a specimen with eyecatching appeal. The gnarled woodgrain character of the exterior makes this piece obviously petrified wood for any novice observer. Check out these knots (shown right) on the outside! It displays perfectly sitting on its natural uncut end (upper right picture). If you like limb casts, don't let this one get away because it is perfect for your display case.
3" x 2" on polished face; 3" Height varies from 1.25" to 3" tall $49

Sycamore (Platanus sp.)
Clarno Formation; Late Eocene
Teater Ranch, near Post Oregon
** What incredible rays this piece exhibits! The deposit of sycamore at Teater Ranch produced considerably more small diameter limbs than it did larger diameter branches suitable for slabbing. So, if you are one of the many collectors who prefer slabs to limbs (yes, they are easier to store and easier to view under the microscope) then here is a great candidate for your collection. It is a medium-sized slab with fantastic radial-grain pattern produced by the white-to-tan medullary rays against the black background. With a microscope one will get a fabulous look at the perfect preservation of vascular structure. Diffuse porous and small, these vessels crowd into most of the space between the medullary rays and they extend from one growth ring to the next. There is hardly any unoccupied space remaining! If you are a slab or microscope enthusiast with an eye for beauty, this one is destined for you and your collection.
5.5” x 3.5” on the polished face; 3/8" thick slab $79

Conifer (Pinales Order)
Miocene Rhyolitic Flow
Badger Flat, near Vya, Nevada
** An end cut with a beautiful polished face and a very nice woody character along the exterior length. It will display very nicely just sitting on its natural bottom side. Click on the photo to see the excellent definition of very tight growth rings. The tight growth rings suggest that the tree was growing on a marginal piece of habitat. A fine addition to any collection.
1.75" x 1.5” on the polished face; 3" maximum thickness $30

Teredo bored driftwood (Incertae sedis)
Saltos Shale Member, Monterey formation Middle Miocene
Santa Barbara Canyon, near Cuyama, California
** Here's a very handsome slab of petrified wood with multiple borings from teredos. The Saltos Shale is mostly marine strata that intertongues with the Lower Miocene mixed marine and terrestrial, Vaqueros Formation. We have offered Vaqueros wood in our inventory in the past and it (of course being terrestrial) never has any teredo tunneling. On the other hand, the Vaqueros wood usually has well-preserved wood structure. In contrast, the Saltos Shale wood does not have preservation of wood anatomy but the fact that it is severely bored by teredos is a good indication that wood in this strata must have floated into an embayment with flood waters and spent considerable time in the water, providing a happy home for the so-called teredo worms. Some of the (quite large) borings are filled with mudstone and some are hollow. Many of them are lined with a thin veneer of chalcedony and a few of them have tiny quartz crystals lining the cavity. The so-called teredo worms are not worms at all; they are gastropods. Their shells have become extremely diminished to the point that they live entirely outside of their shell (in their tunnels), opening and closing the now very tiny bivalve shell to literally gnaw their way through the waterlogged, and thus softened wood. In the early days of seafaring before the invention of iron boats (or the replacement of wooden pleasure craft with fiberglass hulls) the teredos were much hated by sailors who were forced to pull their ships out of water frequently to scrape off the critters before they bored tunnels through the wooden hulls. I've always been amazed that the individual teredos are able to avoid crossing any other individual's track. They almost always exhibit parallel travel patterns as is the case in this specimen where all of the borings are parallel to the axis of the tree. Scientific and decorative!
7" x 5" on polished face; 5/8" thick slab $42

"Cupfern" (Cyathodendron texanum)
Jackson Group - Eocene
South Texas
** Really great piece here -- an ancient ancestor of the living genus Cyathea, a group of over 470 species of giant tree ferns found today in tropical climates. The natural exterior displays nearly a dozen very nice frond bases. Be sure to enlarge the photos to see the level of detail preserved. The early rockhounds thought that the frond bases in these fossils somehow resembled "cups" along the exterior and the name "cupfern" took hold for the fossil. Some rockhounds referred to them as "Fernbuds" because they thought the large frond bases represented "buds" of new ferns. Of course, ferns do not reproduce by budding off of a trunk or rhizome so that name, while perhaps engaging, is completely incorrect in its interpretation. This fossil species was first described by Chester Arnold, one of the most accomplished American paleobotanists of the mid-20th century. The specific epitath, "texanum" is derived from the fact that the fossil was once widely found on the surface and collected on ranches and reservoir margins in south Texas. Today they are much harder to find - the surface materials have been picked up and new specimens are mainly found after rainstorms erode them out of streambanks and gullies. This specimen is a transverse cut through the "false trunk" of the fern. Structures visible on the polished face include vascular bundles, ramentum, frond traces and occasional adventitious roots.
2" x 1" on polished face; false trunk section up to 3.5" long $67