Petrified sycamore wood from Squaw Creek (Washington State, USA)

A rare fossil wood from the North American Miocene forests.

Assortment of petrified sycamore wood cabochons - Washington State, USA

Introduction

The petrified sycamore woods of Squaw Creek, in Washington State (USA), are among the rarest and most sought-after fossil woods by collectors and lapidaries. Dating to the Middle Miocene, these plant fossils bear witness to forests that have long since disappeared and to an environment radically different from the one known today in the Columbia Basin.

At the crossroads of paleobotany, volcanic geology, and lapidary art, these petrified woods represent exceptional material both for scientific study and for the creation of cabochons or high-end decorative objects.

Geological Origin and Age

The fossil woods from Squaw Creek are dated to approximately 15 to 16 million years ago, corresponding to the Middle Miocene. At that time, the region was covered by humid temperate forests crossed by active river systems.

These woods are associated with the sedimentary deposits of the Ellensburg Formation, closely linked to the Columbia River Basalt Group, a vast volcanic province formed by successive basaltic lava flows. These volcanic episodes played a key role by promoting the rapid burial of tree trunks and their long-term preservation.

Petrification Process

The sycamore wood fossilized through siliceous permineralization. After falling or being transported by rivers, the trunks were buried in sediments saturated with silica-rich waters. Gradually:

• the organic matter was replaced by minerals (microcrystalline quartz and chalcedony),

• the anatomical structure of the wood was preserved with remarkable precision,

• the growth rings and the wood grain remained clearly visible.

This mode of fossilization produces a material that is extremely stable, hard, and well suited for polishing.

Détail montrant la structure silicifiée d'un bois de platane.

An Exceptional Fossil Wood: Sycamore

Most petrified woods known worldwide originate from coniferous trees. At Squaw Creek, however, the fossil wood is sycamore (genus Platanus), a broadleaf species that is far rarer in the fossil record.

Identified specimens display:

• an internal texture characteristic of sycamore wood,

• a grain that often becomes very readable after polishing,

• subtle contrasts ranging from light beige to warm brown, sometimes enhanced by gray or honey tones.

This botanical singularity gives the Squaw Creek woods a distinctive status within the world of fossil woods.

Location and Rarity

The Squaw Creek site is located in central Washington State, not far from Kittitas. Access to the historic fossil-bearing areas is now highly restricted, with some sections incorporated into military lands.

This limitation, combined with the natural rarity of the material, explains:

• the small quantity of petrified sycamore wood available on the market,

• the growing interest among collectors,

• the high value placed on well-preserved and well-polished pieces.

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Lapidary and Aesthetic Interest

From a lapidary perspective, petrified sycamore wood from Squaw Creek is particularly appreciated for:

• its good polishing properties,

• the clear readability of the wood structures,

• its natural, understated, and elegant appearance.

It is mainly used for:

• collectible cabochons,

• unique pieces intended for artisanal jewelry,

• decorative objects or display specimens.

Each polished slice reveals a cross-section of geological time, transforming an ancient tree into a true mineral archive.

Scientific and Heritage Value

Beyond their aesthetic value, these fossil woods represent valuable records of:

• Miocene climates in the western United States,

• the evolution of North American temperate forests,

• the interactions between volcanism, sedimentation, and fossilization.

  
  

They therefore contribute to a deeper understanding of the environmental history of the North American continent.

Cabochon made of petrified sycamore wood, from a private collection.

Conclusion

The petrified sycamore wood from Squaw Creek embodies a rare fusion of science, nature, and craftsmanship. Rare, ancient, and aesthetically striking, these specimens are both exceptional fossils and high-quality gemstone materials.

For lovers of minerals, fossils, and natural gemstones, these petrified woods represent much more than just a material: they are a mineralized record of Washington’s Miocene forests.

Bibliographie

Beck, G. F. (1941–1943). Fossil Woods of the Far West. Vol. I, No. 2 (May 1, 1941): Elm and sycamore.

Buurman, P. (1972). Mineralization of fossil wood. Scripta Geologica, 12, 1–43, 38 figs. Leiden.

Dillhoff, T. A. (s.d.). Miocene Woods of Eastern Washington. Part 1: Introduction. Manuscrit / publication institutionnelle.

Mustoe, G. E., & Dillhoff, T. A. (2022). Mineralogy of Miocene petrified wood from Central Washington State, USA. Minerals, 12(2), 131. https://doi.org/10.3390/min12020131

Prakash, U., & Barghoorn, E. S. (1961a). Miocene fossil woods from the Columbia basalts of central Washington, I. Journal of the Arnold Arboretum, 42, 165–199.

Prakash, U., & Barghoorn, E. S. (1961b). Miocene fossil woods from the Columbia basalts of central Washington, II. Journal of the Arnold Arboretum, 42, 347–361.

Prakash, U. (1968). Miocene fossil woods from the Columbia basalts of central Washington, III. Palaeontographica, Bd. 122, 183–200.

Schuster, J. E. (2005). Geologic map of Washington State. Washington Division of Geology and Earth Resources, Geologic Map GM-53, scale 1:500,000.

Washington Geological Survey. (s.d.). Washington Department of Natural Resources. https://dnr.wa.gov/washington-geological-survey

U.S. Geological Survey. (s.d.). National Geologic Map Database – Product description 82898. https://ngmdb.usgs.gov/Prodesc/proddesc_82898.htm