Allchar deposit (alternative spellings Alsar deposit, Alšar deposit or Alshar deposit) is a low-temperature

hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...

gold Gold is a chemical element with the symbol Au (from la, aurum) and atomic number 79. This makes it one of the higher atomic number elements that occur naturally. It is a bright, slightly orange-yellow, dense, soft, malleable, and ductile me ...

–

arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...

–

antimony Antimony is a chemical element with the symbol Sb (from la, stibium) and atomic number 51. A lustrous gray metalloid, it is found in nature mainly as the sulfide mineral stibnite (Sb2S3). Antimony compounds have been known since ancient t ...

–

thallium Thallium is a chemical element with the symbol Tl and atomic number 81. It is a gray post-transition metal that is not found free in nature. When isolated, thallium resembles tin, but discolors when exposed to air. Chemists William Crookes an ...

deposit in

Kavadarci Municipality Kavadarci ( mk, Кавадарци ) is a municipality in the southern part of North Macedonia. ''Kavadarci'' is also the name of the town where the municipal seat is found. Kavadarci Municipality is part of the Vardar Statistical Region. Geogr ...

North Macedonia North Macedonia, ; sq, Maqedonia e Veriut, (Macedonia before February 2019), officially the Republic of North Macedonia,, is a country in Southeast Europe. It gained independence in 1991 as one of the successor states of Yugoslavia. It ...

. For some time, the thallium-rich part of the deposit was mined. The Crven Dol mine yielded

and the ore body still holds estimated amount of 500 t of thallium. The mineral lorandite from this ore deposit can be used to determine the

solar neutrino A solar neutrino is a neutrino originating from nuclear fusion in the Sun's core, and is the most common type of neutrino passing through any source observed on Earth at any particular moment. Neutrinos are elementary particles with extremely smal ...

flux. "Mineral collecting at Allchar is only allowed with permission from the University of Skopje. The area will be declared a protected site. In about 2010, several collectors without this permit were arrested by police."

Geology

The deposit is a

Carlin–type gold deposit Carlin–type gold deposits are sediment-hosted disseminated gold deposits. These deposits are characterized by invisible (typically microscopic and/or dissolved) gold in arsenic rich pyrite and arsenopyrite. This dissolved kind of gold is c ...

, similar to those found in the Carlin Unconformity,

Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the 7th-most extensive, ...

Mining

Mining of

Arsenic Arsenic is a chemical element with the symbol As and atomic number 33. Arsenic occurs in many minerals, usually in combination with sulfur and metals, but also as a pure elemental crystal. Arsenic is a metalloid. It has various allotropes, ...

started in the 15th century when the

Ottoman Empire The Ottoman Empire, * ; is an archaic version. The definite article forms and were synonymous * and el, Оθωμανική Αυτοκρατορία, Othōmanikē Avtokratoria, label=none * info page on book at Martin Luther University) ...

ruled this land.Boev, B., Šorša, A., Boev, I. (2016) Geochemical and mineralogical characteristics of the central part of the Alšar deposit (Republic of Macedonia) with particular reference to investigations by X-ray diffraction. Geologica Macedonica, 30, 115-127. Crven Dol mine operated in the antimony-poor and arsenic- and thallium-rich layer of the orebody. The minerals making most of the orebody are

realgar Realgar ( ), also known as "ruby sulphur" or "ruby of arsenic", is an arsenic sulfide mineral with the chemical formula α-. It is a soft, sectile mineral occurring in monoclinic crystals, or in granular, compact, or powdery form, often in asso ...

orpiment Orpiment is a deep-colored, orange-yellow arsenic sulfide mineral with formula . It is found in volcanic fumaroles, low-temperature hydrothermal veins, and hot springs and is formed both by sublimation and as a byproduct of the decay of anothe ...

, As-bearing

pyrite The mineral pyrite (), or iron pyrite, also known as fool's gold, is an iron sulfide with the chemical formula Fe S2 (iron (II) disulfide). Pyrite is the most abundant sulfide mineral. Pyrite's metallic luster and pale brass-yellow hue giv ...

and

marcasite The mineral marcasite, sometimes called “white iron pyrite”, is iron sulfide (FeS2) with orthorhombic crystal structure. It is physically and crystallographically distinct from pyrite, which is iron sulfide with cubic crystal structure. Both ...

. The deposit was mined extensively between 1880 and 1908. Antimony, arsenic and thallium were produced during that period.

Minerals

Pyrite,

stibnite Stibnite, sometimes called antimonite, is a sulfide mineral with the formula Sb2 S3. This soft grey material crystallizes in an orthorhombic space group. It is the most important source for the metalloid antimony. The name is derived from the ...

, orpiment and realgar are the main minerals forming the ore. Lorandite – a thallium arsenic

sulfosalt mineral Sulfosalt minerals are sulfide minerals with the general formula , where *A represents a metal such as copper, lead, silver, iron, and rarely mercury, zinc, vanadium *B usually represents semi-metal such as arsenic, antimony, bismuth, and rarely ...

with formula TlAsS₂ – is the main thallium mineral in the deposit. Several other thallium minerals have been discovered in the mine over the years, for example, jankovićite (), fangite () and bernardite ().

LOREX

LORandite EXperiment (LOREX) is using lorandite from the ore deposit to determine the

flux. This mineral contains large amounts of

thallium-205 Thallium (81Tl) has 41 isotopes with atomic masses that range from 176 to 216. 203Tl and 205Tl are the only stable isotopes and 204Tl is the most stable radioisotope with a half-life of 3.78 years. 207Tl, with a half-life of 4.77 minutes, has the ...

which undergoes a neutrino capturing reaction and yields lead-205 in the process. The ²⁰⁵Tl(ν_e,e⁻)²⁰⁵Pb process has a relatively low threshold energy of 52

keV Kev can refer to: Given name * Kev Adams, French comedian, actor, screenwriter and film producer born Kevin Smadja in 1991 * Kevin Kev Carmody (born 1946), Indigenous Australian singer-songwriter * Kev Coghlan (born 1988), Scottish Grand Prix moto ...

and thus relatively high efficiency. With the age of the deposit of 4.5 to 4.2 million years, the solar neutrino flux can be estimated over the last 4 million years provided it is possible to determine the amount of lead-205 in a lorandite sample. This reaction can be induced not only by neutrino but other high energy cosmic particles, which all have different penetration depth in the crust. Therefore, a large volume of data is being accumulated during 2008–2010 from different depths of the deposit to produce reliable data.

References

{{Authority control Gold mining Mining in Europe Ore deposits Mineral exploration Geography of Macedonia (region) Geological type localities