Rayite, a

monoclinic In crystallography, the monoclinic crystal system is one of the seven crystal systems. A crystal system is described by three vectors. In the monoclinic system, the crystal is described by vectors of unequal lengths, as in the orthorhombic s ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2 ...

containing

Lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

Silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

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 ...

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 ...

, was found during microscopic and electron microprobe study of specimens from the complex, polymetallic sulphide-native metal sulpho-salt paragenesis of

Rajpura Rajpura () is a city in Patiala district in the Indian state of Punjab, India, situated along the border of the Indian state of Haryana. It is located 26 KM Patiala city, towards East from District Head Quarter. It is Tehsil Head Quarter. Rajp ...

- Dariba,

Rajasthan Rajasthan (; lit. 'Land of Kings') is a state in northern India. It covers or 10.4 per cent of India's total geographical area. It is the largest Indian state by area and the seventh largest by population. It is on India's northwestern s ...

India India, officially the Republic of India (Hindi: ), is a country in South Asia. It is the seventh-largest country by area, the second-most populous country, and the most populous democracy in the world. Bounded by the Indian Ocean on the so ...

. It is named after Dr. Santosh K. Ray of President College,

Calcutta Kolkata (, or , ; also known as Calcutta , List of renamed places in India#West Bengal, the official name until 2001) is the Capital city, capital of the Indian States and union territories of India, state of West Bengal, on the eastern ba ...

. It bears a striking resemblance to owyheeite in terms of its

ratio, yet its structural affinity lies with

Semseyite Semseyite is a rarely occurring sulfosalt mineral and is part of the class of lead antimony sulfides. It crystallizes in the monoclinic system with the chemical composition Pb9Sb8S21. The mineral forms dark gray to black aggregates. Etymology ...

. The average composition is

-47.06,

Copper Copper is a chemical element with the symbol Cu (from la, cuprum) and atomic number 29. It is a soft, malleable, and ductile metal with very high thermal and electrical conductivity. A freshly exposed surface of pure copper has a pinkis ...

-0.03,

-4.54,

-2.04,

-27.42, Sulphur-19.59 by wt.% (total 100.68) suggesting an ideal formula of Pb₈ Sb₈ S₂₁, where Ag > Tl.

Meneghinite Meneghinite is a sulfosalt mineral with the chemical formula CuPb13 Sb7S24. In the orthorhombic crystal system, meneghinite has a Mohs hardness of , one perfect cleavage and a conchoidal fracture. It is a blackish lead-grey in colour and gives a ...

, Owyheeite, and Galena are related

minerals In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid chemical compound with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed ...

Occurrence

It was found in the ores of precambrian polymetallic massive- sulfide deposit interbedded with

kyanite Kyanite is a typically blue aluminosilicate mineral, found in aluminium-rich metamorphic pegmatites and sedimentary rock. It is the high pressure polymorph of andalusite and sillimanite, and the presence of kyanite in metamorphic rocks gener ...

graphite Graphite () is a crystalline form of the element carbon. It consists of stacked layers of graphene. Graphite occurs naturally and is the most stable form of carbon under standard conditions. Synthetic and natural graphite are consumed on lar ...

schists Schist ( ) is a medium-grained metamorphic rock showing pronounced schistosity. This means that the rock is composed of mineral grains easily seen with a low-power hand lens, oriented in such a way that the rock is easily split into thin flakes ...

diopside Diopside is a monoclinic pyroxene mineral with composition . It forms complete solid solution series with hedenbergite () and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull ...

-bearing calc-

silicates In chemistry, a silicate is any member of a family of polyatomic anions consisting of silicon and oxygen, usually with the general formula , where . The family includes orthosilicate (), metasilicate (), and pyrosilicate (, ). The name i ...

, and meta-cherts in Rajpura- Dariba deposit, Udaipur Division,

Udaipur Udaipur () ( ISO 15919: ''Udayapura''), historically named as Udayapura, is a city and municipal corporation in Udaipur district of the state of Rajasthan, India. It is the administrative headquarter of Udaipur district. It is the historic cap ...

District, Dariba Mine,

. It is observed in patches, measuring up to 0.5 mm, reaching a maximum dimension of about 30 μm.

Physical properties

Rayite can occur as individual grains with a tabular habit that can reach a maximum diameter of about 30 um, or as patches up to 0.5 mm.

, owyheeite, and galena are the related

. The mineral is lead grey in colour from a macro perspective, with a metallic lustre and a lead grey streak. Because of its small grainsize and rarity, no cleavage could be observed, and its density could not be calculated. It is also found that rayite is not radioactive. Rayite is a white

with faint bluish and greenish under a microscope. When in touch with galena, it takes on a grey tint; when it grows in between

meneghinite Meneghinite is a sulfosalt mineral with the chemical formula CuPb13 Sb7S24. In the orthorhombic crystal system, meneghinite has a Mohs hardness of , one perfect cleavage and a conchoidal fracture. It is a blackish lead-grey in colour and gives a ...

, it takes on a bluish-greenish tint. Under a microscope, rayite's colour and reflectance resemble owyheeite's, though the latter exhibits a more pronounced red, index, and olive tinge. The mineral's bireflectance is weak in the studied sections, and the colour of reflection

pleochroism Pleochroism (from Greek πλέων, ''pléōn'', "more" and χρῶμα, ''khrôma'', "color") is an optical phenomenon in which a substance has different colors when observed at different angles, especially with polarized light. Backgrou ...

shifts from green to blue-green. Anisotropism is perceptible and appears as dark blue to dark reddish-brown when polarizers are not fully crossed, and no internal reflections are observed.

Chemical composition

Electron microprobe analyses conducted on four grains, revealed the absence of elements with atomic numbers greater than 11. Calculations based on 39 atoms yielded satisfactory results, and the determined ideal formula was expressed as Pb₈ Sb₈ S₂₁. The relationship between

silver Silver is a chemical element with the symbol Ag (from the Latin ', derived from the Proto-Indo-European ''h₂erǵ'': "shiny" or "white") and atomic number 47. A soft, white, lustrous transition metal, it exhibits the highest electrical ...

and

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 ...

remains uncertain due to the available data. Microprobe analyses indicated a slight variation in

ratios, suggesting the potential substitution of

for

. The presence of an excess

metal A metal (from Greek μέταλλον ''métallon'', "mine, quarry, metal") is a material that, when freshly prepared, polished, or fractured, shows a lustrous appearance, and conducts electricity and heat relatively well. Metals are typicall ...

atom Every atom is composed of a nucleus and one or more electrons bound to the nucleus. The nucleus is made of one or more protons and a number of neutrons. Only the most common variety of hydrogen has no neutrons. Every solid, liquid, gas, ...

per unit formula compared to the ideal semseyite formula ( Me₁₇ S₂₁) is deemed noteworthy. Therefore, this implies that it is conceivable for half of the (

) atoms to take the place of

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

sites within the

crystal A crystal or crystalline solid is a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered microscopic structure, forming a crystal lattice that extends in all directions. In addition, macro ...

structure. Simultaneously, the other half could fill the ordinarily unoccupied tetrahedral spaces between the "

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 ...

" chains, resembling the pattern observed in the bismuthite-

aikinite Aikinite is a sulfide mineral of lead, copper and bismuth with formula Pb Cu Bi S3. It forms black to grey or reddish brown acicular orthorhombic crystals with a Mohs hardness of 2 to 2.5 and a specific gravity of 6.1 to 6.8. It was originally fou ...

homologous series. Earlier observations pointed to compositional variations in natural

semseyite Semseyite is a rarely occurring sulfosalt mineral and is part of the class of lead antimony sulfides. It crystallizes in the monoclinic system with the chemical composition Pb9Sb8S21. The mineral forms dark gray to black aggregates. Etymology ...

, indicating an excess of

atoms beyond the stoichiometric composition, with statistical distribution of

atoms within the unit cell. The identification of rayite supported this proposition, suggesting its crystal structure as a "stuffed" derivative of the

crystal.

X-ray crystallography

The material, subject to electron probe analysis, was extracted from a polished section beneath an

ore Ore is natural rock or sediment that contains one or more valuable minerals, typically containing metals, that can be mined, treated and sold at a profit.Encyclopædia Britannica. "Ore". Encyclopædia Britannica Online. Retrieved 7 Apr ...

microscope however fragments suitable for a single

study was not found. Utilizing unfiltered Fe-radiation and a 57.3 mm camera,

X-ray An X-ray, or, much less commonly, X-radiation, is a penetrating form of high-energy electromagnetic radiation. Most X-rays have a wavelength ranging from 10 picometers to 10 nanometers, corresponding to frequencies in the range 30&nb ...

powder diffraction data were obtained. Data showed a significant similarity to those reported for

(

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 ...

, sulphur) however it wasn’t entirely identical. For the X-ray diffraction powder pattern analysis of rayite, cell dimensions were determined as follows: a = 13.603, b = 11.935, c = 24.453 Å, with a β angle of 106.05°, and the

space group In mathematics, physics and chemistry, a space group is the symmetry group of an object in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of an object that leave it uncha ...

C2/c. The resulting lattice constants are approximately a = 13.60 ± 0.02, b = 11.96 ± 0.03, c = 24.49 ± 0.05 Å, with an angle β of 103.94 ± 0.12°.

References

{{Reflist Monoclinic minerals Sulfide minerals Lead minerals Silver minerals Thallium minerals Antimony minerals Minerals in space group 15 Wikipedia Student Program

Occurrence

Physical properties

Chemical composition

X-ray crystallography

See also

References