Limb Cast

Object/Artifact

-

Crater Rock Museum

Name/Title

Limb Cast

Entry/Object ID

78.61.106

Description

Assemblage Zone: sedmentary Chemical Composition: Si O2 Crystal System: Hexagonal Description: Age: Mid-Miocene Location data: Crooked River, Central Oregon John Day Formation Description: Water worn, polished ends show fortified agate in greys with small crystalline center with a surrounding green and brown rock at edges. Outer cast is grey with some greens. Size: Diameter: 2 1/2" Length: 4 1/2" Type of Fossils Present: Plants Fracture: conchoidal Grain Size: Fine Hardness: 7 Quartz Lithofacies: Prineville Basalt 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: 1978.61.106

Dimensions

Dimension Notes

Dimension taken at widest points

Location

Location

Container

Right

Drawer

2nd Shelf

Shelf

Right

Cabinet

Case #100

Wall

South wall

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent