Oregon State Mineral
Garnierite is a generic name for a hydrous nickel silicate important as an ore of nickel. It is not a single mineral, but a mixture of various nickel and nickel-bearing magnesium layer silicates, including serpentine, talc, chlorite, olivine, and others. Garnierite occurs as pale green to bright apple green; darker green varieties of this mineral contain the most nickel.
In Oregon, garnierite forms through surface weathering of rocks that are rich in magnesium and iron. It forms in very wet conditions, for which Oregon is famous.
When nickel mining began on Nickel Mountain, near Riddle, Oregon, in 1953, it meant that the United States was partially independent from foreign sources of this strategic metal. This deposit, containing nickel-rich garnierite, was discovered in 1864, but not mined until nearly a century later. During that time period, only prospecting and initial development were performed. The deposit attracted national attention during World War II. During the war, the United States was obtaining its nickel from Ontario, Canada, which could not provide a supply sufficient to meet Allied war needs.
The Oregon mine, operated by the Hanna Company, was at one time the only nickel mine and smelter in the country. It closed in the 1990s. Oregon does not have an official state mineral, but garnierite is a suitable representative of Oregon’s history, geology, and economy.
This mineral was named for Jules Garnier, a French geologist who first discovered it in New Caledonia in 1864. Almost a century and a half later, the mineral industry of this Pacific island and French territory continues to be dominated by the mining of garnierite and other ores containing nickel.
FORMATION AND OCCURRENCE
Garnierite is commonly found throughout the world in nickel deposits in residual products of rock decay. In addition to its formation through surface weathering of rocks, garnierite also forms through secondary mineralization of igneous rocks. It occurs in masses. The Falcondo mine in the Dominican Republic is a famous locality for this mineral.
The following is a list of garnierite occurrences. Not all are currently mined.
Garnierite is a primary ore of nickel. Nickel is an important mineral, mainly used as an alloy. Stainless steel is the major use of nickel.
Specimens of garnierite are sought by mineral collectors for their color and beauty. Although not particularly well known, garnierite is used as a gemstone.
Chemical Formula: (Ni,Mg)3Si2O5
Crystal Structure: Orthorhombic-dipyramidal
Hardness (Mohs): 2-3
Color: Green, yellowish-green
Habit: Microscopic Crystals
Some data courtesy of the Mineralogical Society of America
Author: World Trade Press