I know in my mind that these dendritic agates are a type of agate with mineral (iron and manganese) inclusions - but this one sure looks like a little fossilized fern. That's why it seems so at home on the ring band with a cast fern. Don't blame me if you don't get much done when you first start wearing this... I've worn it, and it takes a while to quit looking down at it all the time. You can do it....
 
Details:
Dendritic Agate (7/8" x 1/2")
Band: 1/2" wide
Band: Recycled sterling silver
Finish: oxidized
Size: 7.25