Eskolaite is a rare
chromium
Chromium is a chemical element; it has Symbol (chemistry), symbol Cr and atomic number 24. It is the first element in Group 6 element, group 6. It is a steely-grey, Luster (mineralogy), lustrous, hard, and brittle transition metal.
Chromium ...
oxide mineral
The oxide mineral class includes those minerals in which the oxide anion (O2−) is bonded to one or more metal alloys. The hydroxide-bearing minerals are typically included in the oxide class. Minerals with complex anion groups such as the sil ...
(
chromium(III) oxide Cr
2O
3).
Discovery and occurrence
It was first described in 1958 for an occurrence in the
Outokumpu
Outokumpu Oyj is a group of international companies headquartered in Helsinki, Finland, with 10,600 employees in more than 30 countries. Outokumpu is the largest producer of stainless steel in Europe and the second largest producer in the Americ ...
ore deposit of eastern
Finland
Finland, officially the Republic of Finland, is a Nordic country in Northern Europe. It borders Sweden to the northwest, Norway to the north, and Russia to the east, with the Gulf of Bothnia to the west and the Gulf of Finland to the south, ...
.
[ It occurs in chromium bearing ]tremolite
Tremolite is a member of the amphibole group of silicate minerals with composition Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2. Tremolite forms by metamorphism of sediments rich in dolomite and quartz, and occurs in two distinct forms, crystals and fib ...
skarn
Skarns or tactites are coarse-grained metamorphic rocks that form by replacement of carbonate-bearing rocks during regional or contact metamorphism and metasomatism. Skarns may form by metamorphic recrystallization of impure carbonate protoliths, ...
s, metamorphosed
Metamorphic rocks arise from the transformation of existing rock to new types of rock in a process called metamorphism. The original rock (protolith) is subjected to temperatures greater than and, often, elevated pressure of or more, causi ...
quartzite
Quartzite is a hard, non- foliated metamorphic rock that was originally pure quartz sandstone.Essentials of Geology, 3rd Edition, Stephen Marshak, p 182 Sandstone is converted into quartzite through heating and pressure usually related to tecton ...
s and chlorite
The chlorite ion, or chlorine dioxide anion, is the halite (oxyanion), halite with the chemical formula of . A chlorite (compound) is a compound that contains this group, with chlorine in the oxidation state of +3. Chlorites are also known as s ...
bearing veins
Veins () are blood vessels in the circulatory system of humans and most other animals that carry blood towards the heart. Most veins carry deoxygenated blood from the tissues back to the heart; exceptions are those of the pulmonary and fetal c ...
in Finland; in glacial
A glacier (; or ) is a persistent body of dense ice, a form of rock, that is constantly moving downhill under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires ...
boulder clays in Ireland
Ireland (, ; ; Ulster Scots dialect, Ulster-Scots: ) is an island in the North Atlantic Ocean, in Northwestern Europe. Geopolitically, the island is divided between the Republic of Ireland (officially Names of the Irish state, named Irelan ...
and in stream pebbles in the Merume River of Guyana
Guyana, officially the Co-operative Republic of Guyana, is a country on the northern coast of South America, part of the historic British West Indies. entry "Guyana" Georgetown, Guyana, Georgetown is the capital of Guyana and is also the co ...
.[ It has also been recognized as a rare component in chondrite meteorites.][
The mineral is named after the Finnish geologist ]Pentti Eskola
Pentti Elias Eskola (8 January 1883 – 6 December 1964) was a Finland, Finnish geologist who specialised in the petrology of granites and developed the concept of metamorphic facies. He won the Wollaston Medal in 1958, the Vetlesen Prize in 19 ...
(1883–1964).
Structure and physical properties
Eskolaite crystallizes with trigonal symmetry in the space group
In mathematics, physics and chemistry, a space group is the symmetry group of a repeating pattern in space, usually in three dimensions. The elements of a space group (its symmetry operations) are the rigid transformations of the pattern that ...
''R'c'' and has the lattice parameters a = 4.95 Å and c = 13.58 Å at standard conditions. The unit cell contains six formula units. The lattice is analogous to that of corundum
Corundum is a crystalline form of aluminium oxide () typically containing traces of iron, titanium, vanadium, and chromium. It is a rock (geology), rock-forming mineral. It is a naturally transparency and translucency, transparent material, but ...
, with Cr3+ replacing Al3+.
See also
* List of minerals named after people
This is a list of minerals named after people. The chemical composition of the mineral follows the name.
A
* Abelsonite: – American physicist Philip Hauge Abelson (1913–2004)
* Abswurmbachite: – German mineralogist Irmgard Abs-Wurmbac ...
References
Chromium minerals
Oxide minerals
Trigonal minerals
Minerals in space group 167
Hematite group
Minerals described in 1958
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