Perrierite-(Ce)

Chemical formula: Ce₃+₄MgFe₃+₂Ti₄+₂O₈(Si₂O₇)₂

A rare, black sorosilicate mineral, valued by collectors for its well-formed, prismatic crystals.

## Characteristics Perrierite-(Ce) is a complex sorosilicate of titanium, cerium, iron, and magnesium, belonging to the crichtonite group. It typically forms small, prismatic or tabular crystals up to several millimeters long, often terminated by steep faces. It occurs as single crystals or their radial aggregates. Its color is almost always black, and on thin edges, it may be translucent reddish-brown. ## Physical Properties This mineral is characterized by a hardness of 5.5-6 on the Mohs scale and a significant density of approximately 4.4 g/cm³. It has a vitreous to resinous luster. It is brittle, and its fracture is conchoidal or uneven. It does not exhibit cleavage. It is opaque, except for very thin fragments, which may be translucent. ## Colors and Varieties The dominant and essentially only color found for perrierite-(Ce) is black. Thin fragments, when held up to light, may show shades from reddish-brown to brown. No distinct color varieties or commercial varieties are recognized. ## History and Name The name "perrierite" was given in 1950 by the Italian mineralogist Sergio Bonatti in honor of Carlo Perrier (1886-1948), an Italian mineralogist and chemist from the University of Palermo. The suffix "-(Ce)" was added later, in accordance with the rules for naming rare-earth minerals, indicating cerium as the dominant element at a specific site in the crystal structure. The mineral was originally discovered in sands from Nettuno, near Rome, Italy. ## Uses Perrierite-(Ce) has no industrial applications. Its significance is purely scientific and as a collector's item.

Properties

Mohs hardness: 5.5-6
Luster: Vitreous to resinous
Streak: Red-brown
Density: 4.3-4.48
Cleavage: None
Fracture: Conchoidal to uneven
Transparency: Translucent in thin splinters, Opaque
Crystal system: Monoclinic

Diagnostic features

## Identification Perrierite-(Ce) is identified by its black color, vitreous or resinous luster, and characteristic prismatic crystals. Its high density is also a helpful diagnostic feature. A reddish-brown streak distinguishes it from many other black minerals. ## Distinguishing from Similar Minerals Perrierite-(Ce) is difficult to distinguish from the closely related crichtonite-(Ce) and aenigmatite without advanced studies (e.g., X-ray diffraction). Visually, it can be confused with ilmenite, which has a similar color and luster but a different crystal habit and a black streak. It can also be mistaken for schorl tourmaline, which, however, often exhibits striations on crystal faces and has a lower density. ## Crystal Forms Crystals are typically elongated, prismatic, often flattened tabular. They occur as single, attached crystals or form radial and stellate aggregates embedded in the host rock.

Geological environment

## Genesis Perrierite-(Ce) is a mineral of magmatic origin. It occurs as an accessory mineral in alkaline extrusive rocks, such as trachytes and phonolites, and in associated tuffs and volcanic ashes. It is also found in syenites and carbonatites. ## Mineral Associations This mineral co-occurs with other minerals typical of alkaline environments, such as sanidine, nepheline, aegirine, arfvedsonite, eudialyte, astrophyllite, as well as titanite, apatite, and magnetite. ## Localities Key localities for perrierite-(Ce) worldwide include the original locality in Nettuno near Rome, Italy. Significant specimens also come from the Ilimaussaq igneous complex in Greenland, the Khibiny Massif on the Kola Peninsula in Russia, and Mont Saint-Hilaire in Quebec, Canada. It also occurs in Norway and the USA (Colorado).

Rarity

Rare

For collectors

## Quality Criteria Most valued by collectors are specimens with sharply terminated, lustrous crystals of distinct, prismatic form. Radial aggregates where individual crystals are clearly visible are also highly prized. Contrast with a lighter host rock (e.g., white nepheline) significantly enhances the visual appeal of the specimen. Crystal size is crucial – specimens exceeding one centimeter in length are rare and sought after. ## Popular Localities Localities such as Mont Saint-Hilaire in Canada and the Khibiny Massif in Russia are considered classic and provide the best specimens. Specimens from these locations are characterized by good crystal development and often occur in attractive associations with other rare minerals.

Care and storage

## Cleaning Perrierite-(Ce) specimens should be cleaned very carefully. It is best to use a soft brush to remove dust. If necessary, the specimen can be rinsed with distilled water and then thoroughly dried. Ultrasonic cleaners should not be used. ## What to Avoid The mineral is sensitive to strong acids, which can damage it. Avoid sudden temperature changes and prolonged exposure to direct sunlight, although its distinct effect on the mineral is not known. Due to its brittleness, it should be protected from impacts and falls. ## Storage Collector's specimens of perrierite-(Ce), especially those with well-formed crystals, should be stored in separate, padded boxes or on stands to prevent scratches and mechanical damage. It is best to keep them in stable room conditions, away from moisture and dust.

Sources

IMA Mineral List (CNMNC)