Ekebergite

Chemical formula: Th₄+Fe₂+Nb₅+₂O₈

Ekebergite is a disqualified name for a variety of scapolite, which is no longer recognized as a distinct mineral species.

## Characteristics Ekebergite is a historical name that was used to describe certain varieties of minerals from the scapolite group. It is no longer recognized by the International Mineralogical Association (IMA) as a distinct mineral species. Specimens historically referred to as ekebergite are in fact scapolites, most commonly from the marialite-meionite isomorphic series. The appearance of these specimens is typical for scapolite – they form prismatic crystals, often columnar or tabular in habit, as well as granular and massive aggregates. ## Physical Properties As ekebergite is a scapolite, its physical properties are identical to those of scapolite. Hardness on the Mohs scale ranges from 5 to 6. The luster is vitreous, and on fracture surfaces, it can be resinous. The mineral is usually translucent to opaque. Density varies depending on the chemical composition within the marialite-meionite series, typically within the range of 2.5-2.8 g/cm³. ## Colors and Varieties Specimens historically called ekebergite were most often white, gray, greenish, or yellowish. This name did not refer to a specific color variety but was a synonym for scapolite from certain localities, especially from Scandinavia. ## History and Name The name "ekebergite" was introduced in 1832 by Jöns Jacob Berzelius in honor of the Swedish chemist Anders Gustaf Ekeberg, the discoverer of tantalum. This name referred to material originating from Norway and Sweden. In later years, with the development of analytical techniques, it was determined that ekebergite is in fact scapolite, which led to the discrediting of this name as a distinct mineral species.

Properties

Mohs hardness: 5-6
Luster: Vitreous to resinous
Streak: White
Density: 2.5-2.8
Cleavage: Good on {100} and {110}
Fracture: Uneven to conchoidal
Transparency: Transparent to opaque
Crystal system: Tetragonal

Diagnostic features

## Identification As a scapolite, ekebergite is characterized by prismatic crystals with a square or octagonal cross-section. It often exhibits fluorescence under ultraviolet light, usually in shades of yellow, orange, or pink. Hardness (5-6) and characteristic vitreous luster are also helpful in identification. ## Distinguishing from Similar Minerals Scapolite is sometimes confused with quartz, feldspars, or beryl. It is distinguished from quartz by its lower hardness and the presence of cleavage. It differs from feldspars by its square crystal cross-section (feldspars have rectangular or rhombic cross-sections). Unlike beryl, scapolite is usually less hard and often fluoresces. ## Crystal Forms Scapolite forms elongated, prismatic crystals, often terminated by bipyramids. It also occurs in acicular, granular, and massive aggregates.

Geological environment

## Genesis Scapolites (including specimens formerly called ekebergite) are typical metamorphic minerals. They form as a result of regional and contact metamorphism of calcium-rich rocks, such as limestones, marls, and argillaceous shales. They also occur in skarns, gneisses, amphibolites, and as a product of hydrothermal alteration of plagioclase in igneous rocks. ## Mineral Associations It coexists with minerals such as calcite, diopside, vesuvianite, garnets (mainly grossular and andradite), epidote, titanite, and plagioclase. ## Localities Historical ekebergite specimens mainly originated from localities in Norway (Arendal area) and Sweden. As scapolite, this mineral is widely distributed worldwide, with known occurrences including Canada (Quebec, Ontario), USA (New York, Massachusetts), Brazil, Madagascar, Tanzania, and Myanmar.

Rarity

Common

For collectors

## Quality Criteria Since "ekebergite" is a historical name for scapolite, the evaluation criteria are identical to those for scapolite. The most valued are well-formed, transparent crystals with intense color (especially yellow, purple, or pink). Crystal size, lack of damage, and aesthetic association with other minerals (matrix) are also important. Specimens exhibiting strong fluorescence or a cat's eye effect are additionally sought after.

Care and storage

## Cleaning Scapolite specimens (formerly ekebergite) can be cleaned with lukewarm water and a mild soap, using a soft brush. Ultrasonic cleaners should be avoided, as they can damage specimens with internal fractures. ## What to Avoid Scapolite is sensitive to strong acids, so contact with chemicals should be avoided. It should also not be subjected to rapid temperature changes. ## Storage Specimens should be stored in separate boxes or on a soft surface to prevent scratching by harder minerals. It does not require special conditions regarding light or humidity.

Sources

IMA Mineral List (CNMNC)