Gary Green Jasper

Gary Green Jasper, also known as larsonite, is a green picture jasper from Oregon, USA, formed from silicified (petrified) fossil wood. It is celebrated for olive to forest-green backgrounds threaded with crisp black manganese dendrites that look like distant trees and shrubs.

Named after rockhound Gary Larson who popularized the material, it is a hard, opaque microcrystalline quartz. Its strong green color is unusual among scenic jaspers and makes it a standout lapidary stone.

Gary Green Jasper began as ancient wood buried in volcanic sediment in Oregon. Silica-rich groundwater infiltrated the wood and surrounding material, replacing organic tissue molecule by molecule with microcrystalline quartz in a process called permineralization.

Iron and other impurities tinted the silica green, while manganese-bearing solutions later crystallized along fractures to form the black dendrites. The result is a fully silicified stone that preserves the toughness of jasper while retaining scenic, sometimes wood-grain-like, internal structure.

Look for an opaque jasper with distinctive olive to forest-green fields, often with cream zones and sharp black dendritic trees.

• Hardness: 6.5-7; scratches glass.
• Luster: waxy raw, vitreous polished.
• Streak: white.
• Look-alikes: other green jaspers and chrysoprase can resemble the base color, but Gary Green's combination of muted green with black dendrites and its fossil-wood origin are diagnostic. Some pieces show faint wood grain that confirms its petrified-wood source.

Gary Green Jasper is a prized lapidary stone, cut into cabochons, slabs, and pendants that display its green scenery and dendrites. Quality larsonite is collectible and increasingly scarce.

At near 7 Mohs it is durable and polishes well for everyday jewelry. As both a jasper and petrified wood, it carries metaphysical associations with grounding, growth, and ancient time, which are traditional beliefs rather than scientific facts.