Sulfidic travertine from the upper Cenozoic of Indonesia.

This attractive material is called "Bumblebee Jasper" or "Mustard Jasper", in reference to its color. "Jasper" is a rockhound/lapidarist term for finely crystalline quartz, but Bumblebee Jasper is not quartz - it bubbles in acid. Chemical analysis has confirmed that it is calcium carbonate (CaCO3 - calcite). The coloration is from various microscopic mineral inclusions. The light to medium gray areas are ~inclusion-free calcite. The dark gray to black bands are from pyrite inclusions (FeS2 - iron sulfide, also known as "fool's gold"). The yellowish and orangish areas are from realgar inclusions. Realgar is a reddish-colored arsenic sulfide mineral (AsS). In the form of very small, disseminated inclusions, it has a yellowish-orangish color.

Bumblebee Jasper has a finely-, but irregularly-banded structure. The calcite itself is fibrous. Banded, fibrous calcareous rocks are known as travertine, which is a chemical sedimentary rock. Travertine is commonly encountered in caves, in the form of speleothem - stalactites, stalagmites, columns, flowstone, etc. Travertine also forms at many hot springs. Bumblebee Jasper appears to be travertine deposited in a volcanic solfatara area, with signficant iron, arsenic, and sulfur impurities.

The deposit is reported to be near the base of Mount Papandayan, a subduction zone stratovolcano in Indonesia.

Locality: unrecorded/undisclosed site near Mount Papandayan, western Java, Indonesia

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