Characteristics of Arsenic

Arsenic is a gray metal with the chemical symbol As. As a pure metal, arsenic is semi-metallic and very brittle. Arsenic reacts rapidly with air, tarnishing and oxidizing into arsenous oxide. When heated, arsenic sublimes forming ferrous sulfide. It is a strengthening alloy with other metals, although tends to be soft in pure form. Arsenic does not melt, but sublimes directly into gas at high temperatures. It is a poor conductor. Arsenic is poisonous. Arsenic is used predominantly as a pesticide treatment for wood. Pure arsenic is rare on Earth, although arsenic is commonly bound with other elements as various minerals found across the globe. Arsenic is commonly in the minerals listed in table 1.

Mineral Name	Chemical Formula	Specific Gravity	As %
Arsenopyrite	FeAsS	6.19 gm/cc	46.01
Safflorite	(Co,Fe)As2	7.48 gm/cc	72.04
Glaucodot	(Co,Fe)AsS	6.22 gm/cc	45.37
Skutterudite	CoAs3	5.95 gm/cc	76.09
Realgar	AsS	3.60 gm/cc	70.03
Orpiment	As2S3	3.49 gm/cc	60.90

Table 1: Minerals containing the element Arsenic

Uses of Arsenic

Arsenic was used in ancient times as a poison, as an alloy to strengthen bronze, and even as a topical to lighten skin. Although widely used in historic times, health and environmental concerns have led to more limited modern use. Today, arsenic is considered a "critical mineral" in domestic metallurgical applications that serve defense, energy, and telecommunications technologies (Fortier and others, 2018). It is primarily used as a pesticide for preserving lumber (pressure treated wood) and for various agricultural chemicals. Arsenic compounds are used to make components in semi-conductors for electronics, photovoltaics, telecommunications, aerospace research, and biomedical applications. This element is also used as an alloy to harden lead in car batteries, and as an alloy with other metals to reduce corrosion and improve strength.

Arsenic Geology

Arsenic is common in the Earth's crust, bound with other elements to form a variety of minerals. Arsenic-bearing minerals may form within igneous intrusive or metamorphic rocks. Hydrothermal environments including hot springs, certain volcanic environments, and areas of contact metamorphism may host arsenic-bearing minerals. Arsenic may also form in igneous pegmatite rocks. Arsenic is often associated with metallic or sulfide deposits such as gold and copper ores.

Mineral System	Deposit Type	Geologic Provinces
Arsenide	Post-magmatic arsenopyrite in greisen	Blue Ridge

Table 2: Prospective arsenic mineral systems, deposit types (Hofstra and Kreiner, 2020), and geologic provinces in Virginia

Arsenic in Industry

Arsenic is often obtained as a smelting byproduct of copper, gold, iron, and lead. Arsenic is largely mined in China and Morocco (USGS, 2020). The U.S. does not maintain a supply of arsenic in the National Defense Stockpile and is 100 percent import reliant from several countries including China, Morocco, Japan, and Belgium. Arsenic has not been produced in the United States since 1985. Concerns related to the mining and production of arsenic include release of arsenic into soil and water where contamination is a serious health issue.

In Virginia, although arsenic may exist within many sulfide deposits, only one arsenic mine has produced historically. The arsenic discovered and mined in the Commonwealth is associated with other sulfide or metallic minerals and elements such as pyrite, gold, copper, iron, cobalt, and nickel. These sulfide ores can be found in veins, or irregularly distributed throughout the hosted metamorphosed volcanic or magmatic rocks.

Floyd County

Arsenic was discovered in Floyd County as early as 1882 (Hess and Graton, 1911). Production did not occur until the construction of the Brinton Mine near Huffville in 1902 (Hess and Graton, 1911; Luttrell, 1966). Primarily within the Lynchburg gneiss, the arsenic is found as arsenopyrite intergrown with pyrite occurring in lenticular veins and disseminations. The ore body is 3 to 14 feet thick and reaches a depth of 120 feet. In 1902, a processing plant was built at the mine site and between the years 1903 and 1917, the mine produced up to 100 tons of arsenic (Luttrell, 1966; Young, 1956). The arsenic produced here was used to manufacture insecticides (Hess and Graton, 1911). The processing mill was dismantled in 1919 and mining has not recurred since (Luttrell, 1966).