Chalcedony comes in many colors from the common tannish-grey often found on rock outcrops to greens and purples, reds and tans. People have given separate names to the various colors – bloodstone when there is spotted red (guess where that name comes from), carnelian when a bright red, a dirty brown chert when the quartz mineral is mixed with clay, bright apple-green chrysoprase, and jasper which is generally opaque. The naming is subjective – but these stones are among the oldest used in jewelry and some named as birthstones. You can find out more about the various types of silica in the Quartz: By Any Other Name.
Chalcedony, Jasper, and Agate are only three forms of very, very fine-grained quartz – the crystals are there, but so tiny that it exhibits none of the crystal shape – just the hardness of quartz with a translucent luster. Agate is banded or shows other structures and chalcedony is generally non-banded. Jasper is generally opaque due to inclusion of clay. The names are not important – they are made of the elements silica and oxygen, and each has the mineral structure of quartz.
Hesse, Reinhard. “Silica Diagenesis: Origin of Inorganic and Replacement Cherts.” Earth Science Reviews, 1989. https://doi.org/10.1016/0012-8252(89)90024-X
Pabian, R., Jackson, B, Randy, P and J Cromartie, 2006,Agates, Treasures of the Earth,Firefly Books, 184 pp.
Oregon, United States
After extrusive rocks form on the surface of the earth, rain falls onto them and filters down through the rock. The water dissolves minerals along the way and redeposits other minerals in other places. Silica, in the form of microcrystalline quartz, is often the product of this process. This jasper, colored a warm caramel brown to dark red formed in this way in volcanic rock. It is known as the Owyhee Jasper and is from the Owyhee Canyon, known for its complex markings. Larger pieces are known as ‘picture jasper’.
The history of the name of Owyhee Canyon is interesting. Several crew members of either Captain Cook or Captain Van Couver or an anonymous fur trader hailed from Hawaii came along on the expedition – probably glad to get off the ship for a few days. They liked the area and settled there – and Owyhee is more like ‘Hawaii’ is an nineteenth century spelling for Hawaii.