Lueshite

Chemical formula: NaNb⁵⁺O₃

Lueshite is a rare, black sodium niobium oxide from the perovskite group, discovered in the Democratic Republic of Congo.

## Characteristics Lueshite is a rare mineral from the perovskite group, being a sodium niobium oxide. It forms small, cubic or pseudo-octahedral crystals, which are usually opaque and black. On thin edges, they may appear reddish-brown when translucent. It occurs as single crystals or small aggregates within the host rock. ## Physical Properties This mineral is characterized by a hardness of 5.5 on the Mohs scale, placing it in the same category as apatite. It has a relatively high density of 4.44 g/cm³. The luster is described as metallic to submetallic. It is generally opaque, although thin fragments can be translucent. ## Colors and Varieties The dominant color of lueshite is black. Thin crystal edges or very fine fragments may exhibit reddish-brown translucency. No named varieties of this mineral are distinguished. ## History and Name Lueshite was first described in 1959 by the Russian mineralogist Alexander Safiannikoff. Its name comes from its discovery locality – the Lueshe mine in the Democratic Republic of Congo (then Belgian Congo), which remains its type locality. ## Uses Due to its rarity, lueshite has no industrial applications. It is solely an object of interest for collectors specializing in rare minerals, mineralogical systematics, or minerals of the perovskite group.

Properties

Mohs hardness
5.5
Luster
Metallic
Streak
gray
Density
4.44
Cleavage
{001}, imperfect
Fracture
Uneven
Transparency
Translucent,Opaque
Crystal system
Orthorhombic

Diagnostic features

## Identification Lueshite is identified by its black color, metallic luster, relatively high density, and characteristic cubic crystal form. A gray streak is also an important diagnostic feature. Its occurrence in carbonatites is a key field indicator. ## Distinguishing from Similar Minerals Lueshite can be confused with other black, metallic minerals found in similar environments, such as magnetite, pyrochlore, or ilmenite. It is distinguished from magnetite by its lack of magnetic properties. Distinguishing it from pyrochlore, which often forms octahedra, may require chemical analysis (EDS/XRD) to confirm its composition (dominance of sodium and niobium). Ilmenite has a different chemical composition (titanium and iron) and crystallizes in the trigonal system. ## Crystal Forms Lueshite crystals are usually small and cubic, often with modified corners. They can also take on a pseudo-octahedral form. They occur as single, well-formed crystals embedded in the host rock.

Geological environment

## Genesis Lueshite is an igneous mineral, crystallizing in a specific type of rock known as carbonatites. It forms in the late stages of crystallization of these carbonate- and rare-element-rich intrusions. Its presence is associated with sodium metasomatism processes. ## Mineral Associations This mineral co-occurs with other minerals typical of carbonatites. In its type locality, it was found in association with calcite, phlogopite, pyrochlore, and various minerals from the apatite group. ## Localities The most important and historical occurrence of lueshite is its type locality – the Lueshe mine in North Kivu province in the Democratic Republic of Congo. It is also known from several other carbonatite complexes worldwide, including the Kovdor complex on the Kola Peninsula in Russia and the Oka complex in Quebec, Canada.

Rarity

Very rare

For collectors

## Quality Criteria The most prized specimens by collectors are those with sharp, well-formed crystals of distinct cubic shape and strong luster. Contrast with a light host rock (e.g., white calcite) is important. Crystal size is a key factor – specimens with crystals exceeding a few millimeters are already considered significant. ## Popular Localities By far the most desirable and classic specimens come from the type locality in Lueshe, DR Congo. Specimens from the Kola Peninsula (Russia) also appear on the market, although they often have a less ideal form.

Care and storage

## Cleaning Lueshite specimens should be cleaned very carefully, using a soft brush to remove dust. If necessary, distilled water can be used, followed by thorough drying of the specimen. Ultrasonic cleaners should be avoided. ## What to Avoid This mineral is sensitive to strong acids. Contact with household and laboratory chemicals should be avoided. It should not be subjected to sudden temperature changes. ## Storage Lueshite is best stored in separate, padded display boxes to prevent scratching by harder minerals. It is not sensitive to light, but protection from dust and humidity is advisable.

External references

Sources

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