1" Purple Cubic Fluorite Crystals on Arsenopyrite - Yaogangxian Mine

The Yaogangxian mine is a tungsten-tin deposit in the Nanling Mountains of Hunan, China. The mine field is about 4 x 2.5 kliometers (2.5 x 1.5 miles) and includes two primary deposits: the Yaogangxian quartz vein-type tungsten-tin deposit, and the Heshangtan skarn-type tungsten-tin deposit.

The Yaogangxian deposit (with minor greisen-style mineralization) has been mined since 1914 and hosts minor copper, tungsten, silver, lead, zinc, and bismuth minerals. The Heshangtan deposit has been mined since the 1960s and hosts a variety of associated silver ores. Both of these deposits are a result of the Mesozoic Yaogangxian pluton, composed of biotite-granite, porphyritic granite and quartz porphyry, which intruded into Cambrian-Devonian sediments and Jurassic limestones.

A variety of high quality mineral specimens are collected from this site. Some of the most popular minerals include arsenopyrite, bismuthinite, manganese-bearing calcite (manganocalcite), chalcopyrite, ferberite, fluorite, hübnerite, molybdenite, pyrite, rhodochrosite, siderite, stibnite, topaz, and tungstite.

Arsenopyrite is an iron arsenic sulfide with the chemical formula FeAsS. It is the most common arsenic-bearing mineral and is its principal ore, and can be found in igneous, metamorphic and sedimentary rock. Crystals can be found as prismatic, twinned, columnar, elongated and massive formations within veins and are found in locations all around the world. Depending on minerals present during formation, the iron in arsenopyrite can be replaced by cobalt, forming cobaltite.

Arsenopyrite contains a significant amount of poisonous arsenic, making it somewhat toxic. Washing hands following handling is recommended.