New Mexico Mineral Symposium — Abstracts

The Franklin mine stands out worldwide in unique characterization. By today's standards the mine was relatively small in size. However, in every other respect, it was truly a giant.

It was the richest zinc deposit ever encountered by man, having produced over 22,000,000 tons of ore averaging 19.6% zinc. During peak periods of production it employed nearly 1,000 men and fostered a mining town that was a model community for the rest of the industry. Even during the Great Depression of the 1930s it remained in operation. Its ores played host to the most complex diversification of minerals on Earth.

Its origin is interpreted as exhalative belches rich in zinc, iron and manganese that emanated from deep inside the planet's mantle. The protore fluids oozed out of an ancient sea-floor rift well over a billion years ago. The epoch events experienced across the next eon, age after age, during cataclysmic periods of geophysical change and geochemical alteration, provided unique opportunity for the development of one of nature's greatest mineralogical treasures.

Even in its most fundamental sense, Franklin demonstrates its unique nature. Here, unlike other zinc mines worldwide, the ore consists of silicates (willemite) and oxides (zincite and franklinite). The presence of iron and manganese is not at all insignificant.

To date, this deposit, along with its twin at nearby Sterling Hill, boasts of over 350 mineral species. This is more than 10% of those known to man, more than anywhere else on Earth. Of the 350, nearly seventy were first described from here, and nearly half of those are found nowhere else. Over half of the minerals found here exhibit fluorescence under ultraviolet irradiation. This uncom¬mon phenomenon has earned Franklin the indisputable title of The Fluorescent Mineral Capital of the World."