Name/Title
Limb CastEntry/Object ID
78.61.59Description
Limb Cast
Eocene
Clarno Formation
Crooked River, Crook Co., OR
Assemblage Zone: tropical to subtropical
Chemical Composition: Si O2
Crystal System: Hexagonal
Description: Age: Tertiary
Location data: Clarno Formation, Hampton Butte, Eastern Oregon USA
Description: Polished side shows open crystalline center in grey and white surrounded by dark blue grey fortified agate with some white at some points along outer edge. Outer rock is in clay like beige and greenish material. Surface cracks seen.
Size: Diameter: 5 1/4" Length: 3"
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 CollectionAcquisition
Accession
78.61Source or Donor
Delmar Smith Limb Cast CollectionAcquisition Method
DonationOther Names and Numbers
Other Number
Other Number: 1978.61.59Dimensions
Dimension Notes
Dimension taken at widest points.Location
Location
Display Case
PW-13Room
Petrified Wood RoomBuilding
Crater Rock MuseumCategory
ExhibitDate
October 16, 2025Notes
Location added when performing inventory
