Arsenic (As) is a typ­i­cal acces­so­ry ele­ment in many geo­chem­i­cal and met­al­lo­genic sys­tems. It is wide­ly present in the form of arsenides, sul­foarsenides, and oxide–sulfide min­er­als that occur with­in ores of non-fer­rous, rare, and pre­cious met­als. Although arsenic has rel­a­tive­ly lim­it­ed direct indus­tri­al use as a stand­alone ele­ment, its pres­ence in ores is of sig­nif­i­cant min­er­alog­i­cal, geo­chem­i­cal, and tech­no­log­i­cal impor­tance — as an indi­ca­tor of ore-form­ing con­di­tions and as an envi­ron­men­tal­ly sen­si­tive com­po­nent dur­ing ore pro­cess­ing.

Arsenic ores is includ­ed in the list of min­er­als of nation­al impor­tance, approved by Res­o­lu­tion of the Cab­i­net of Min­is­ters of Ukraine No. 827 of Decem­ber 12, 1994, as non-fer­rous met­al ores.

General information

From a geo­chem­i­cal per­spec­tive, arsenic is a chal­cophile and lithophile ele­ment capa­ble of form­ing its own min­er­als (real­gar, orpi­ment, arsenopy­rite) as well as enter­ing iso­mor­phi­cal­ly into the crys­tal struc­tures of lead, cop­per, sil­ver, cobalt, and oth­er met­al min­er­als. Its con­cen­tra­tions often increase in zones of sec­ondary enrich­ment and under con­di­tions of low-tem­per­a­ture hydrother­mal activ­i­ty.

Grow­ing inter­est in arsenic is dri­ven not only by its pres­ence in ores as a harm­ful impu­ri­ty but also by its poten­tial as a recov­er­able com­po­nent with­in inte­grat­ed ore-pro­cess­ing tech­nolo­gies. In geo­log­i­cal and indus­tri­al analy­sis, arsenic is regard­ed as an ele­ment reflect­ing redox con­di­tions, tem­per­a­ture, degree of min­er­al­iza­tion, and the physic­o­chem­i­cal evo­lu­tion of hydrother­mal sys­tems.

Genetic types of deposits

In Ukraine, arsenic occurs as an asso­ci­at­ed com­po­nent in ores of cobalt, cop­per, mer­cury, bis­muth, and oth­er met­als. Its pres­ence is typ­i­cal of hydrother­mal vein deposits, meta­so­mat­ic zones, as well as oxi­dized zones of mer­cury and gold deposits. Arsenic min­er­als may also occur in asso­ci­a­tion with pre­cious met­als, espe­cial­ly under con­di­tions of arsenide-type min­er­al­iza­tion.

1. Arsenic–Cobalt asso­ci­a­tion
Arsenic is a typ­i­cal com­pan­ion of cobalt in arsenide–sulfide ores. Main min­er­als include saf­florite ((Co,Fe,Ni)AsS), skut­teru­dite (CoAs₃), arsenopy­rite (FeAsS), and lollin­gite (FeAs₂). These min­er­als form under low- to medi­um-tem­per­a­ture hydrother­mal con­di­tions. Such par­a­ge­net­ic asso­ci­a­tions are char­ac­ter­is­tic of vein and meta­so­mat­ic deposits. Sim­i­lar min­er­al­iza­tion may occur in the Ukrain­ian Shield, par­tic­u­lar­ly with­in arsenic occur­rences in the Kirovohrad region.
2. Arsenic–Copper asso­ci­a­tion
In cop­per sul­fide-rich ores, arsenic may be incor­po­rat­ed into min­er­als such as tetra­hedrite (Cu₁₂S­b₄S₁₃, with iso­mor­phic sub­sti­tu­tion of Sb by As), enar­gite (Cu₃AsS₄), and “luzonite” (CuAsS). These min­er­als are found in zones of sec­ondary enrich­ment and in high-tem­per­a­ture hydrother­mal sys­tems. Such asso­ci­a­tions are com­mon in poly­metal­lic deposits of the Carpathi­an region.
3. Arsenic–Mercury asso­ci­a­tion
In hydrother­mal mer­cury deposits, arsenic often occurs togeth­er with cinnabar (HgS), form­ing real­gar (As₄S₄) and orpi­ment (As₂S₃) as com­mon com­pan­ions. This asso­ci­a­tion is typ­i­cal for mer­cury deposits in Don­bas and Tran­scarpathia (e.g., the Myky­tiv­ka deposit). Arsenic plays an impor­tant role in mer­cury geo­chem­istry, influ­enc­ing min­er­al sta­bil­i­ty and migra­tion behav­ior.
4. Arsenic–Bismuth asso­ci­a­tion
Rare arsenic–bismuth asso­ci­a­tions include bis­muth arsenides (BiAs, BiAsS) and bis­muthi­nite (Bi₂S₃), which some­times occur in com­plex vein deposits con­tain­ing gold or tel­lurides. These are char­ac­ter­is­tic of ultra­m­eta­mor­phic or post-mag­mat­ic con­di­tions. Such occur­rences have been iden­ti­fied with­in the Azov and Dnieper megablocks.

Uses of arsenic and its compounds

Arsenic and its com­pounds have a wide, though rel­a­tive­ly lim­it­ed in vol­ume, range of appli­ca­tions across var­i­ous indus­tries. The largest share of con­sump­tion is attrib­uted to the chem­i­cal, met­al­lur­gi­cal, and elec­tron­ics indus­tries, with arsenic tri­ox­ide (As₂O₃) serv­ing as the pri­ma­ry start­ing mate­r­i­al for most tech­ni­cal prod­ucts.

• In met­al­lur­gy, arsenic is used as an alloy­ing ele­ment to impart increased hard­ness, cor­ro­sion resis­tance, and brit­tle­ness to alloys. It is added to lead-based alloys, bronzes, and cer­tain spe­cial­ty mate­ri­als, par­tic­u­lar­ly in the pro­duc­tion of bat­ter­ies, bear­ings, and ammu­ni­tion.
• In the semi­con­duc­tor indus­try, com­pounds such as gal­li­um arsenide (GaAs) and oth­er arsenides are wide­ly used in high-fre­quen­cy elec­tron­ics, light-emit­ting diodes, laser diodes, and space-grade solar cells. Gal­li­um arsenide is a strate­gi­cal­ly impor­tant mate­r­i­al in micro­elec­tron­ics due to its high­er speed per­for­mance and ther­mal sta­bil­i­ty com­pared to sil­i­con.
• In the chem­i­cal indus­try, arsenic com­pounds are used in the pro­duc­tion of dyes, pig­ments, glass, and cer­tain her­bi­cides, roden­ti­cides, and anti­sep­tics. How­ev­er, due to its high tox­i­c­i­ty, the use of arsenic in house­hold chem­i­cal prod­ucts has been sig­nif­i­cant­ly restrict­ed or com­plete­ly banned in many coun­tries.
• In med­i­cine, arsenic has a his­tor­i­cal­ly impor­tant but now niche appli­ca­tion. Organ­ic arsenic com­pounds (such as arsenic tri­ox­ide-based prepa­ra­tions) are used as sec­ondary treat­ments for cer­tain forms of leukemia and par­a­sitic infec­tions. In the past, arsenic was a basis for many “med­i­c­i­nal” prod­ucts, but its tox­i­co­log­i­cal prop­er­ties have great­ly lim­it­ed mod­ern use.
• In agri­cul­ture, arsenic-con­tain­ing com­pounds were for­mer­ly used as insec­ti­cides and seed treat­ments. Due to their eco­tox­i­c­i­ty and long-term accu­mu­la­tion in soils, these sub­stances have been phased out in most coun­tries world­wide.