Enhydros are commonly known as "water agate" and are quite a remarkable sight to see. They are agates that have a sealed bubble of water inside. Some specimens have more than a single bubble, some have partially-filled pockets of water that will move, while still others have the water in a stable position. A second--more exotic--type of enhydro is a geode in which the chemically-rich liquid inside is no longer forming crystals because of a lack of pressure or temperature. Only in the first, smaller type of enhydro is the liquid actually visible. It is this type of specimen we are looking for.
Most of these agates are about three-quarters of an inch in diameter or smaller, although a few have been found up to 2" long. I have only found a couple over an inch.
Typically they are light gray to yellow-gray in color and have to be removed from a host rock. A hammer and chisel are needed to carefully chip the local enhydro from a basalt outcrop. The enhydros have a thin "rind" of agate and must be tumbled to see the bubbles clearly. Great care must be taken in the tumbling process to prervent the removal of too much material which will allow the liquid to escape and destroy the value of the specimen. I suggest using 220 grit silicon carbide and checking the progress daily. Once the bubble is clearly visible, tumble-polish in cerium oxide.
Enhydros can be found in two locations in our area, both near Kalama along the Columbia River.
( 1 ) From 1-5 take the Kalama exit under the freeway. At the stop sign turn right, then left on the first street. At the next stop turn left again and you will be heading north out of town. The outcrops are on the northeast edge of Kalama.
(2) Take the Kalama River road 1.3 miles east of town to the Madrona Road. Follow this road l/2 mile to the Spencer Creek road. 1.2 miles up this road you will find a basalt outcrop on the left side of the road. It is easy to spot as a lot of little holes have been chipped in the basalt to remove the small enhydros. All basalt outcroppings in the area should be searched, especially those that might occur further from the roadways.
While it takes some searching--and some slow, careful chiselling--to find the small enhydros, they are scarce enough (and pretty enough) to be a valuable addition to your mineral collection.