Information about Arsenic

Native arsenic – arsenic in its pure elemental form rather than combined with other elements – is a relatively uncommon mineral, though arsenic itself is widespread in nature and found in a great many other minerals. It is one of the most historically notorious substances on earth, with a reputation stretching from ancient poisons to Victorian medicine cabinets.

It most commonly occurs as rounded, botryoidal (grape-like) masses or crusts, and occasionally as stalactitic forms with concentric internal banding. Well-formed crystals are exceptionally rare. It is typically tin-white on a fresh surface, but tarnishes almost immediately on exposure to air to dark grey or near-black. It has a metallic lustre and is noticeably heavy for its size.

Native arsenic is found in hydrothermal mineral veins – that is, veins formed by hot mineral-rich fluids moving through fractures in rock – where it typically occurs alongside silver, cobalt, nickel, and antimony minerals. It is closely related to native antimony and native bismuth, and the three minerals share a similar structure. Arsenic and antimony can form a natural alloy known as stibarsen (formerly called allemontite), and some specimens show layered bands of the two minerals side by side.

Uses and History

Arsenic has one of the longest and most colourful histories of any mineral. It was known to the ancient Egyptians and Greeks – the philosopher Theophrastus described two arsenic-bearing minerals, orpiment and realgar, around 300 BC – and has been used, misused, and feared ever since.

During the Bronze Age, arsenic was alloyed with copper to produce arsenical bronze, a harder material than tin bronze and widely used before tin became the preferred alloy. It has also been used for centuries as a poison – so effectively that it earned the nickname “inheritance powder” in parts of Europe, due to its colourless, near-tasteless nature and the difficulty, historically, of detecting it in a body.

Curiously, arsenic also had a long life as a medicine. In the Victorian era, a preparation known as Fowler’s Solution – essentially arsenic dissolved in water – was a widely prescribed tonic used to treat everything from skin complaints to anaemia, and was reportedly used by Charles Dickens among many others. In the same period, some women in the Austrian Alps are documented to have eaten small amounts of arsenic regularly, believing it improved their complexion and stamina. Arsenic-based compounds continued to be used in medicine into the 20th century, and are still used today in the treatment of certain forms of leukaemia.

In more modern industrial applications, arsenic is used as a semiconductor dopant in electronics, in the production of certain types of glass, in wood preservatives, and historically as a pesticide – though many of these uses are now heavily restricted or banned due to its toxicity.

The discovery of the element itself is generally attributed to Albertus Magnus, who isolated it in around 1250 AD. Its name comes from the Greek arsenikon and the Latin arsenicum, both derived ultimately from a Persian word meaning “yellow orpiment.” The name has been in use in English since at least the 14th century.

Notable localities for collectable native arsenic specimens include Jáchymov in the Czech Republic, which has produced the finest and largest crystals known; Příbram, also in the Czech Republic; Schneeberg, Freiberg, and Sainte-Marie-aux-Mines in the mining districts of Germany and Alsace, France; and the Cobalt mining district of Ontario, Canada. Native arsenic has been recorded from numerous localities in the United Kingdom, including in Cornwall and in parts of Wales.

Mineralogy

Hazards and Warnings

Toxic mineral: arsenic and all of its compounds are poisonous. Prolonged or repeated skin contact should be avoided, and specimens should be stored safely away from children and food preparation areas.

Mineral collectors should wash their hands thoroughly after handling specimens, to avoid any exposure to potential toxins.

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis. When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

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