Editorial Feature

Arsenic – Occurrence, Properties, and Distribution

Sep 26 2013

The element arsenic takes its name from the Latin word “arsenicum” or the Greek word “arrenikos” meaning masculine, alluding to the mineral’s potent properties.

Properties of Arsenic

The following are the key properties of arsenic:

Cell Data
- Space group: R3m (synthetic)
- a = 3.7598(1)
- c = 10.5475(2)
- Z = 6
Crystal Data
- Hexagonal
- Point group: 3 2/m
- Commonly granular, massive, and in concentric layers
- May be reticulated, reniform, stalactitic
- Rarely columnar or acicular
- As rhombohedra, to 1 mm
- Twinning: Rare on twin plane {1014}; pressure twinning on {0112} develops delicate lamellae
- X-ray powder pattern: 2.771 (100), 3.52 (30), 1.879 (30), 2.05 (20), 1.556 (10), 1.768 (10), 1.757 (7)

Chemical Composition

Elements	Content 1	Content 2
As	98.14	99.1
Sb	1.65	0.2
S	0.16	-
insol.	0.15	-
Total	100.10	99.3

Optical Properties
- Pleochroism: Feeble.
- Anisotropism: Distinct, yellowish brown and light gray to yellowish gray
- R1–R2: (400) 56.0–57.5, (420) 55.1–56.8, (440) 54.2–56.2, (460) 53.3–55.8, (480) 52.7–55.7, (500) 52.4–55.7, (520) 52.0–55.7, (540) 51.7–55.7, (560) 51.5–55.6, (580) 51.2–55.4, (600) 51.0–55.2, (620) 50.8–55.0, (640) 50.6–54.9, (660) 50.5–54.8, (680) 50.4–54.7, (700) 50.4–54.6

Estimated Properties

Electron density	Bulk density (electron density) = 5.06 g/cm³ note: Specific gravity of arsenic = 5.74 g/cm³
Photoelectric	PE_Arsenic = 73.21 barns/electron U=PE_Arsenic x ρ electron density= 370.20 barns/cm³
Fermion index	Fermion index = 0 Boson index = 1
Radioactivity	Arsenic is not radioactive

How to Identify Arsenic

Arsenic as a mineral can be identified in the field by its lead gray, gray, and white color variations. Its opaque form has {0001} perfect cleavage. This mineral has a metallic luster with black streak. The fracture of this mineral is uneven. The density of arsenic is 5.7 g/cm³ with a hardness of 3.5 –approximate to a copper penny. It is non-fluorescent and non-magnetic.

Global Distribution

Arsenic is distributed in the following places:

Germany - From Freiberg, Schneeberg, Johanngeorgenstadt, Marienberg, and Annaberg, Saxony; Wolfsberg and St. Andreasberg, Harz Mountains; and Wieden, Black Forest
Czech Republic -At Jachymov (Joachimsthal), Pribram, and Cinovec (Zinnwald)
France- In the Gabe-Gottes mine, Rauenthal, near Sainte-Marie-aux-Mines, Haut-Rhin
Romania - From Sacarimb (Nagyag), Hunyad, and Cavnic (Kapnikbanya)
USA - At Sterling Hill, Ogdensburg, Sussex Co., New Jersey and Washington Camp, Santa Cruz Co., Arizona
China - From the Dajishan tungsten deposits, Jianxi Province
Borneo - At Bidi, Sarawak Province
Japan- In the Akatani mine, Fukui Prefecture
Peru -In the Huallap´on mine, Pasto Bueno, Ancash Province

Occurrence of Arsenic and Useful Mineral Association

Arsenic occurs in hydrothermal veins and deposits that contain other arsenic minerals. It may also occur in Co–Ag sulfide veins. It is often associated with minerals such as arsenolite, realgar, orpiment, stibnite, cinnabar, galena, pyrite, sphalerite, and barite.