Limb Cast

Object/Artifact

-

Crater Rock Museum

Name/Title

Limb Cast

Entry/Object ID

78.61.63

Description

Limb Cast Eocene Clarno Formation Crooked River, Crook Co., OR Assemblage Zone: tropical to subtropical Chemical Composition: Si O2 Crystal System: Hexagonal Description: Age: Eocene Location data: Clarno Formation, Hampton Butte, Eastern Oregon USA Description: Delmar Smith says this is an unusual cast because the body of the cast shows small limb extensions at the outer edge (four total), appearing as knobs. Polished end shows "Half Moon" shaped crystalline center in white and grey, surrounded by fortified agate in blue greys. A hole is seen at one side. Outer cast is in beige and tan. Showing distinct grain. Size: Diameter: 3 3/4" Length: 3 3/8" Type of Fossils Present: Plants Fracture: conchoidal Grain Size: Fine Hardness: 7 Quartz Lithofacies: volcaniclastic Luster: Glassy Occurrence: Like petrified wood, limb cast are created in much the same manner. Volcanic ash or silica-rich sediment buries a tree limb, the limb decays, leaving behind an open void. This void works as a mold that fills with amorphous silica that has percolated through the surrounding rock. Once microamorphous silica has filled the mold and the crystallization process to a (quartz)chalcedony or opal is complete, the result is a siliceous rock with the same exterior markings as the original limb. Pressure: Low-Moderate Rock Color: Light Rock Origin: Post-depositional Rock Type: Sedimentary Specific Gravity: 2.6 Surface Process: Not apparent Streak: white Temperature: Low Texture: Microcrystalline Variety: Petrified woods here are hydrous microcrystalline variety of quartz that can be generally termed as chalcedony or opal.

Collection

Petrified Wood Collection

Acquisition

Accession

78.61

Source or Donor

Delmar Smith Limb Cast Collection

Acquisition Method

Donation

Other Names and Numbers

Other Number

Other Number: 1978.61.63

Dimensions

Dimension Notes

Dimension taken at widest points.

Location

Location

Container

Left

Drawer

Top Shelf

Shelf

Center

Cabinet

Case #100

Wall

South wall

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent