Gadolinite-(Nd)

Chemical formula: Nd<sub>2</sub>Fe<sup>2+</sup>Be<sub>2</sub>O<sub>2</sub>(SiO<sub>4</sub>)<sub>2</sub>

Neodymium, iron, and beryllium silicate; a rare, black mineral from the gadolinite group, found in pegmatites.

## Characteristics Gadolinite-(Nd) is a mineral from the gadolinite group, in which neodymium is the dominant rare-earth element in its composition. It belongs to the silicates. It typically forms poorly developed crystals, embedded in rock, with a prismatic habit, or occurs as irregular grains and massive aggregates. Its surface may be covered with a dull, brownish crust resulting from weathering. It is a heavy and hard mineral. ## Physical Properties The Mohs hardness of gadolinite-(Nd) is 6.5-7. It is characterized by a vitreous luster, often greasy or resinous on fracture surfaces. It is a brittle mineral, with a conchoidal or uneven fracture. It is usually opaque, and only in very thin splinters can it be translucent. Its density is significant, approximately 4.86 g/cm³. ## Colors and Varieties This mineral is black, pitch-black, sometimes with a brownish or greenish tint. No color or commercial varieties are distinguished. ## History and Name The name "gadolinite" honors the Finnish chemist and mineralogist Johan Gadolin, who was the first to isolate yttrium oxide from a mineral of this group. The suffix -(Nd) indicates the dominance of neodymium in the chemical composition and was officially approved by the International Mineralogical Association (IMA) in 1986. The type locality (locus typicus) is the Åskagen quarry in the Västmanland region of Sweden. ## Applications Due to its extreme rarity, gadolinite-(Nd) has no industrial applications. It is solely an object of scientific interest and a prized acquisition for specialized collectors of rare-earth minerals.

Properties

Mohs hardness
6.5-7
Luster
Vitreous to greasy
Streak
Greenish-gray
Density
4.86
Cleavage
Indistinct/poor on {100}
Fracture
Conchoidal to uneven
Transparency
Translucent on thin edges to opaque
Crystal system
Monoclinic

Diagnostic features

## Identification Helpful features for identifying gadolinite-(Nd) include its black color, vitreous to greasy luster, high density, conchoidal fracture, and characteristic occurrence environment—granitic pegmatites. The streak is greenish-gray. This mineral does not exhibit fluorescence. ## Distinguishing from Similar Minerals Distinguishing gadolinite-(Nd) from other minerals in its own group—gadolinite-(Y) and gadolinite-(Ce)—is impossible without advanced chemical analysis (e.g., EDS, WDS). Visually, it is very similar to other black, heavy pegmatite minerals such as allanite, samarskite, euxenite, or fergusonite. Certain identification requires specialized analytical equipment. ## Crystal Forms Gadolinite-(Nd) crystallizes in the monoclinic system. It rarely forms well-developed, single crystals in the form of thick, prismatic columns. Most often, it is found as irregular grains embedded in rock or massive aggregates without distinct crystal faces.

Geological environment

## Genesis Gadolinite-(Nd) is an igneous mineral, crystallizing in the late stages of magma differentiation. It forms in granitic and syenitic pegmatites, rich in rare-earth elements. ## Mineral Associations This mineral occurs in association with other rare-earth minerals such as allanite, monazite, xenotime, as well as with zircon, fluorite, titanite, biotite, microcline, albite, and quartz. ## Localities This is an extremely rare mineral, known from only a few localities worldwide. The most important and type locality is the Åskagen quarry in Västmanland, Sweden. Its occurrence has also been confirmed in the Buer pegmatite in Bjørkedalen, Norway.

Rarity

Very rare

For collectors

## Quality Criteria For collectors, specimens with well-formed, even if small, crystals are of the highest value. Due to the rarity of the mineral, even amorphous fragments are valuable, provided their identity has been confirmed by chemical analysis. Specimens of gadolinite-(Nd) in association with other rare pegmatite minerals are also highly prized. ## Popular Localities Almost all specimens available on the collector's market come from the type locality—the Åskagen quarry in Sweden. Specimens from any other confirmed locality would be considered unique.

Care and storage

## Cleaning Gadolinite-(Nd) specimens should be cleaned very carefully, using a soft brush to remove dust. For heavier dirt, distilled water can be used. Avoid vigorous scrubbing, which could damage the surface of the crystals. ## What to Avoid This mineral is sensitive to strong acids. It should not be subjected to sudden temperature changes. The use of ultrasonic cleaners is not recommended, as vibrations can cause cracking along internal fractures, especially in metamict specimens (with a structure damaged by radiation). ## Storage It is recommended to store specimens in separate, padded boxes or display cases to prevent them from scratching other minerals. Protect from dust and moisture. Exposure to strong sunlight is not advisable, although there is no evidence of its particular harmfulness.

Sources

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