What is menilite opal?

Menilite opal is a type of opal that originates from Slovakia. It is a dark-colored opal that typically has a black or brown base color with flashes of color such as green or blue. It is named after the town of Menilite, where it was first discovered in 1837. Menilite opal is formed from volcanic ash that has undergone a process of chemical alteration in the presence of water. This process results in the formation of silica gel, which eventually becomes opal. Menilite opal is known for its unique, almost wood-like pattern and its durability. It is often used in jewelry-making and has become a popular gemstone in recent years.