The chrysanthemum stone is approximately 270 million years old. It is a dark grey to black limestone matrix with andalusite crystals taking on the appearance of a chrysanthemum. It contains more than 10 kinds of trace elements, such as selenium, strontium, gold, silver, & bismuth.
The black rock itself is a piece of limestone. Limestones are generally lighter in colour, this one is black because of the presence of substantial amounts of organic carbon. This rock is Permian in age, from a time when many areas that today make up China were offshore or underwater plateaus.
The white pattern on the rock is formed of crystals of celestine (or celestite), a strontium-sulphate mineral. Celestine commonly forms elongate crystals of the form seen here, although these are fairly rare in that they’re so thin and on the surface of another rock.
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