This is a perfectly natural piece of sulfur from the Ijen Volcano in East Java, Indonesia. She is 3.3 oz, 2.65” and 2.3” by 21.3”. The Ijen volcano is known for its sulfur production and the sulfur is collected and sold in large chunks although this one is rather small compared to those that are sold. The sulfur here is bright yellow with inclusions of magnesium. She is quite beautiful and a bit lighter than the pictures.
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Natural Yellow Sulfur - Ijen Volcano