Chevkinite-(Ce)

Chemical formula: Ce₃+₄(Ti₄+,Fe₂+,Fe₃+)₅O₈(Si₂O₇)₂

A dark, almost black silicate from the chevkinite group, rich in cerium and titanium, forming prismatic crystals in igneous rocks.

## Characteristics Chevkinite-(Ce) is a mineral from the chevkinite group, belonging to silicates. Its name indicates the dominance of cerium as a rare-earth element. Typical specimens are dark brown to black and opaque, with a resinous or vitreous luster. It forms elongated, prismatic crystals, which often occur as radial aggregates. This mineral is brittle and has an uneven, conchoidal fracture. ## Physical Properties Chevkinite-(Ce) is characterized by a Mohs hardness of 5 to 6. Its density is relatively high, ranging from 4.3 to 4.65 g/cm³, which is a result of the presence of heavy elements such as cerium and titanium. The luster is most often resinous to vitreous. It is an opaque mineral. ## Colors and Varieties This mineral is usually black, less commonly dark reddish-brown or brown. There are no distinct color varieties or commercial types; its identification is primarily based on chemical composition. ## History and Name The name "chevkinite" comes from the surname of the Russian general Konstantin Vladimirovich Chevkin (1802-1875), chief of staff of the mining corps. The mineral was first described in 1839 by Gustav Rose based on material from the Ilmen Mountains in the Russian Urals. The suffix "-(Ce)" was added later according to the rules for naming minerals with a dominant rare-earth element, in this case, cerium. ## Uses Chevkinite-(Ce) has no direct industrial applications. Due to its content of rare-earth elements and titanium, it may be of scientific interest as an indicator of geological processes. For collectors, it represents an interesting, though not visually spectacular, example of a rare-earth silicate mineral.

Properties

Mohs hardness: 5-6
Luster: Vitreous to resinous
Streak: Brownish-gray
Density: 4.3-4.65
Cleavage: Indistinct on {100}
Fracture: Uneven to sub-conchoidal
Transparency: Opaque, thin fragments translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Chevkinite-(Ce) can be identified by its black or dark brown color, resinous luster, and relatively high density. Prismatic, often elongated crystals are also characteristic. It occurs in specific igneous rocks, such as syenites and alkaline granites. ## Distinguishing from Similar Minerals It can be confused with other black, heavy minerals, such as ilmenite, magnetite, tourmaline (schorl), or allanite. It differs from ilmenite and magnetite by the lack of magnetic properties and lower hardness. From schorl, it differs by greater density and different crystal habit (lack of typical tourmaline striations). Distinguishing it from allanite-(Ce) is the most difficult and often requires advanced chemical analyses (EDS/WDS), as both minerals have a similar appearance, physical properties, and often co-occur. ## Crystal Forms Crystals are usually prismatic, tabular, or elongated. They often form radial or chaotic aggregates. They also occur as granular masses in the host rock.

Geological environment

## Genesis Chevkinite-(Ce) is an igneous mineral, crystallizing in the late stages from magmas rich in alkalis and rare-earth elements. It forms in plutonic igneous rocks, such as nepheline syenites, alkaline granites, and associated pegmatites. It can also occur in volcanic tuffs formed from the ashes of such magmas. ## Mineral Associations It often co-occurs with other minerals rich in rare-earth elements and titanium. Typical associated minerals include nepheline, albite, microcline, arfvedsonite, aegirine, titanite, apatite, zircon, and allanite-(Ce). ## Localities The most important and classic localities, from which well-formed crystals originate, are the Ilmen Mountains in the Urals, Russia (type locality). Other known localities include the Kola Peninsula in Russia, alkaline complexes in Norway (Langesundsfjorden area), Sweden (e.g., in Västmanland), and also in the USA (Colorado, Virginia, New Mexico). It also occurs in Greenland and Canada (Quebec).

Rarity

Not very common

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, sharp, and undamaged crystals with a distinct luster. Large, freestanding crystals are rare and command higher prices. The attractiveness is also enhanced by the contrasting placement of black chevkinite crystals on a light rock matrix, for example, on white albite or nepheline. ## Popular Localities Specimens from classic localities, such as the Ilmen Mountains in Russia or the Langesundsfjorden area in Norway, are particularly sought after due to their historical significance. Well-formed crystals from American localities, e.g., from Colorado, are also popular.

Care and storage

## Cleaning Specimens should be cleaned only dry, using a soft brush to remove dust. Water and any chemical agents should be avoided, as the mineral may be sensitive to moisture and react with chemicals. ## What to Avoid Avoid contact with water, acids, and other liquids. The mineral is brittle, so it must be protected from impacts and falls. It should not be heated or exposed to sudden temperature changes. ## Storage It is recommended to store specimens in a dry place, in closed boxes or display cases, to protect them from dust and mechanical damage. Due to its brittleness, it is best stored separately from harder minerals.

Sources

IMA Mineral List (CNMNC)