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.
Translucent actinolite is rare, but can be faceted into gemstones if found in a sufficient quality.