Tag Archives: Clackamas Clarno Formation

Opal, Agate and Petrified Wood

Opal -Volcanic Mineralogy

The Opal and Agate rocks as well as the petrified wood used in the jewelry designs are comprised of quartz. These were formed during the early to mid Tertiary Time in the Eocene era, 50-37 million years ago.

blue opal necklace charm and earrings set
Oregon Opal Jewelry

The Opal and Agate used in the jewelry are from Oregon and what is know as the “Clarno” Type Formation. Clarno formations are characteristic of volcanic mudflows that overlapped and suffocated sedimentary rocks, coastal swamps, and tidal marshes and responsible for rock formations such as Andesites, Rhyolites (Volcanic Wildfire made of ash), and Basalts. These flows also created coal mines from decomposed vegetation, as in peat moss. They also buried and filled hollows and cavities in sedimentary or continental rocks. Most of the Opal and Agate used in the jewelry designs are either filled hollow cavities or tree limb casts from the Clackamas Clarno Formation. When hollow rock cavities were being filled by a layering of minerals it created the visual banding effect and separated them into the opal and agate layers with a chalcedony outer rind.

Agate Limb Casts and Cavities

Oregon Opal Dangle Earrings with Jade and Blue Lace Agate
Oregon blue Opal Agate and Jade

Limb casts and cavity mineral used in the designs are almost entirely comprised of a Chalcedony Agate skin or rind surrounding a translucent-like dichroic luster of  Blue Oregon Opal which will turn solid white if allowed to be exposed to oxygen and light after a short period of time. Clackamas Opals must be maintained to protect the opalescence quality. Although similar to the famed Awapuhi Opals and Thunder Eggs containing opal, agate, and chalcedony found at nearby mines that are of variable quality, the Clackamas formation is quite beautiful and unique.

Petrified Wood Mineralogy

opalized wood
Petrified Wood
Matching Necklace and Earring Set

Just north of the Clackamas Clarno Formation and nearby the Awapuhi Opal mine in Washington State, is the Ginko Petrified Forest. Here, a volcanic mudflow of Pillow Bassalt from the Miocene Era that is 2 miles deep, burried and filled hollow tropical Ginko trees. The mineral Silica, basically water, flowing within the volcanic mudflow adheares to the plant cell walls first and then fills the caivites. The trees turned to stone when they were sealed off from oxygen under the mud.

Petrified Wood Necklace Charm Chehalis River Washington State
Petrified Wood Necklace Charm
Chehalis Washington State