By Chisom Ibemere
Willemite is a zinc silicate mineral and a minor ore of zinc that was first discovered in the 19th century by Dutch scientist Hendrik Willem van Rijgersma. The mineral was named “willemite” in his honor. It is typically found in zinc ore deposits and is closely associated with other zinc minerals such as franklinite and zincite.
Willemite can be found in various locations around the world, including the United States (New Jersey, New York, and Arizona), Mexico, Germany, Belgium, Italy, Austria, and Namibia. One of the most famous willemite occurrences is the Franklin Mine in New Jersey, which is known for its exceptional fluorescent and phosphorescent willemite specimens.
Willemite is primarily used as a collector’s gemstone or mineral specimen due to its fluorescent and phosphorescent properties. It emits a bright green fluorescence when exposed to ultraviolet light, making it popular among collectors. It is also occasionally used as a minor zinc ore.
Willemite occurs in a variety of colours in daylight in fibrous masses and apple green gemmy masses. It is typically green, but can also be yellow, brown, or red in colours. It has a Trigonal crystal system with a hardness of 5.5-6.5 on the Mohs scale. It has a Vitreous to resinous lustre with a white streak and density of 3.87-4.19 g/cm3.
The value of willemite can vary depending on factors such as its color, transparency, fluorescence, and size. High-quality fluorescent specimens with intense green fluorescence are generally more valuable.
However, due to its relative abundance, willemite is not considered a highly valuable gemstone compared to others.