
Here in Northern California, one of the more common collectible stones around is Actinolite. I've always had a soft spot for this mineral, ever since I was a child.
The name "actinolite" comes from the Greek word aktis, meaning "ray" - a reference to the appearance of the crystals.
It is a softer, more fibrous relation to Nephrite Jade, and can commonly be found in regions that have jade or serpentine. The crystals are usually green, ranging from pale green to nearly black - the coloration is determined by the amount of iron the specimen contains. More iron causes darker colors.

In Mendocino County, California, actinolite can commonly be found in most rivers and creeks. The crystals will be worn smooth, but usually when you break them open, lovely bladed crystals will be exposed. When the sun is out, it can be easy to spot the specimens because of the way the sunlight reflects off each fibrous crystal blade - the rock seems to sparkle.
Translucent actinolite is rare, but can be faceted into gemstones if found in a sufficient quality.
Translucent actinolite is rare, but can be faceted into gemstones if found in a sufficient quality.