A crust of altered stone
In the hills of Kachin State, jadeite boulders are covered by a thick, colored crust known as a weathering rind. This is not a separate layer of sediment, but the chemically altered outer part of the jadeite itself. The process begins when rainwater, made slightly acidic by atmospheric carbon dioxide, seeps into microscopic cracks in the stone. This triggers hydrolysis, a chemical reaction that slowly breaks down the hard sodium aluminum silicate (NaAlSi₂O₆) of the jadeite.
The intense rainfall of Myanmar's tropical monsoon climate accelerates this chemical assault. Over immense timescales, the durable pyroxene minerals are converted into softer, secondary clay minerals like kaolinite and gibbsite. Iron and other elements present in the jadeite oxidize, essentially rusting. This process stains the rind with colors ranging from yellow and reddish-brown to black, a feature miners call "skin". These rinds can be several centimeters thick, representing a direct physical record of the stone's long exposure to the elements. The inner, unaltered stone remains the translucent green or white jade valued for millennia.