Limb Cast

Object/Artifact

-

Crater Rock Museum

Name/Title

Limb Cast

Entry/Object ID

78.61.21

Description

Assemblage Zone: sedimentary Chemical Composition: Si O2 Crystal System: Hexagonal Description: Age: Mid-Miocene Location data: Crooked River County, Near Prineville in Central, Oregon, USA John Day Fm. Description: Polished side shows a faded white fortified line inside a light blue agate mass on one side and green mineral deposit on the other side, containing some black. Size: side cut 1.7/8" x 3 1/8" - cast 2.75 x 3 1/8 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: 1978.61.21

Dimensions

Dimension Notes

Dimensions taken at widest points

Location

Location

Container

Center

Drawer

2nd Shelf

Shelf

Right

Cabinet

Case #100

Wall

South wall

Building

Mentzer Hall - Petrified Wood Room

Category

Permanent