Name/Title
Limb CastEntry/Object ID
78.61.125Description
Assemblage Zone: ash flow tuffs
Chemical Composition: Si O2
Crystal System: Hexagonal
Description: Age: Miocene
Location data: John Day Formation, Crooked River, Central Oregon
Description: Polished end shows large crystalline fortified agate center in white, light grey, surrounding by darker grey and some green & red rock at edges.
Size: Diameter: 5 1/4" Length: 1 1/2"
Type of Fossils Present: Plants
Fracture: conchoidal
Grain Size: Fine
Hardness: 7 Quartz
Lithofacies: rhyolitic ash flow
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: 1978.61.125Dimensions
Dimension Notes
Dimension taken at widest pointsLocation
Location
Shelf
2nd shelf right, 2nd shelf rightWall
right - southRoom
Wood roomBuilding
Mentzer Hall - Petrified Wood RoomCategory
PermanentMoved By
Catherine BoydDate
March 6, 2008Location
Container
CenterDrawer
BottomShelf
RightCabinet
Case #100Wall
South wallBuilding
Mentzer Hall - Petrified Wood RoomCategory
Permanent
