Green ‘smithsonite’ from Indonesia appears to be garnierite (falcondoite) in quartz
Recently, ‘new’ material appeared on the market from Indonesia: green crustal deposits and crystals in fissures in yellow-brown rock. Commonly sold under the name “smithsonite,” but also as “garnierite with druzy quartz” and “aragonite in limonite”. Much discussion arose among buyers and sellers about the correct designation, so time for an analysis.
After a brief analysis of my own, it quickly became clear that it was in no way smithsonite or aragonite, but probably quartz combined with an unknown green mineral. To be 100% sure, I sent a piece to the lab for analysis. The green mineral was chemically identified at the lab using EDX analysis as falcondoite in quartz. Falcondoite is a hydrated magnesium-nickel silicate. But without analysis of the crystal structure, it is more appropriate to summarize the mineral with a number of similar magnesium-nickel minerals under the term “garnierite”.
Minerals from the ‘garnierite mix,’ such as falcondoite, are formed in part by weathering in tropical regions of ultramafic (often olivine-bearing) rocks such as komatiite, serpentinite, dunite, peridotite and ophiolite. The “garnierite” minerals often occur in combination with various crystallized silica (chalcedony, quartz) as filled veins and cavities in the weathered parent rock (laterite). This nickel-containing laterite is found, among others, in the Soroako deposit in Sulawesi, Indonesia. Nickel-containing laterite is an important nickel ore and is used in the production of stainless steel, among others.
So what should it be called now?
Briefly, the best description of these stones is the following: garnierite with quartz in nickel-containing laterite.
Courtesy of:
- Yannis Stoneworld for providing a sample
- Pierre Maurizot, geologist at the Geological Survey of New Caledonia, for interpretation of the EDX analysis and the origin of these rocks, see also his extensive article
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