Whittakerite

Chemical formula: NaNa(Mg₂AlFe₃+Li)Si₈O₂₂(OH)₂

Whittakerite is an extremely rare mineral from the amphibole group, characterized by its complex chemical composition and occurrence in fibrous aggregates.

## Characteristics Whittakerite is a very rare, complex silicate belonging to the amphibole supergroup. It typically forms fibrous or asbestiform aggregates, with individual crystals appearing as blades or needles. It is a transparent to translucent mineral with a vitreous luster. ## Physical Properties This mineral has a Mohs hardness of 5.5. Its density is estimated at approximately 3.11 g/cm³. It exhibits perfect cleavage in two directions, typical for amphiboles. ## Colors and Varieties Whittakerite occurs in shades from colorless to pale green. No named varieties have been distinguished. ## History and Name The mineral is named in honor of Eric J. W. Whittaker (1922–2008), a British crystallographer and mineralogist who made significant contributions to the study of amphibole group minerals, including their structure and classification. The mineral was officially recognized by the International Mineralogical Association (IMA) in 2004. ## Uses Due to its extreme rarity, whittakerite has no industrial applications and is solely an object of scientific and collector interest.

Properties

Mohs hardness: 5.5
Luster: Vitreous
Streak: White
Density: 3.11
Cleavage: Perfect on {110}
Fracture: Uneven
Transparency: Transparent to translucent
Crystal system: Monoclinic

Diagnostic features

## Identification Field identification of whittakerite is practically impossible due to its rarity and resemblance to other amphiboles. Definitive identification requires advanced analytical methods, such as X-ray diffraction (XRD) and electron microprobe analysis (EMPA), to determine its exact composition and unit cell parameters. ## Distinguishing from Similar Minerals Whittakerite is visually indistinguishable from many other fibrous amphiboles, such as tremolite, actinolite, or other minerals from its own subgroup (e.g., ferro-whittakerite). Differentiation relies solely on precise chemical analysis, especially the ratio of sodium, magnesium, aluminum, iron, and lithium. ## Crystal Forms This mineral forms elongated, bladed, or acicular crystals, which most often occur as felted, fibrous, or asbestiform aggregates.

Geological environment

## Genesis Whittakerite forms as a result of metamorphic processes. It has been identified in carbonate-silicate rocks (carbonatites) and in calcitic marbles that have undergone contact metamorphism under amphibolite facies conditions. ## Mineral Associations This mineral co-occurs with other minerals typical of metamorphic rocks, such as calcite, dolomite, fluorite, phlogopite, titanite, apatite, zircon, allanite-(Ce), as well as other amphiboles, e.g., from the hornblende group. ## Localities The only confirmed and detailed described occurrence of whittakerite (type locality) is the Poudrette quarry, located on Mont Saint-Hilaire in the Montérégie region, Quebec, Canada.

Rarity

Extremely rare

For collectors

## Quality Criteria The quality of a whittakerite specimen is primarily determined by its scientific value and confirmed identity. Since this mineral is identifiable only through advanced techniques, the most important criterion is reliable analytical documentation confirming its composition. From a visual standpoint, specimens with clearly formed, even if small, crystals may be more desirable than just felted aggregates. ## Popular Localities The only source of whittakerite specimens is its type locality – the famous Poudrette quarry at Mont Saint-Hilaire in Canada. This is one of the most renowned mineralogical localities in the world, famous for the occurrence of hundreds of rare and unique minerals.

Care and storage

## Cleaning Given its fibrous nature and potential fragility, specimens should be cleaned very carefully. Compressed air is recommended for dust removal. If necessary, a soft brush can be used, avoiding strong pressure. Contact with water should be limited. ## What to Avoid Avoid contact with acids and other aggressive chemicals. The mineral is brittle, so it must be protected from impacts and vibrations. It should not be cleaned in ultrasonic cleaners. ## Storage Whittakerite specimens, especially those with a fibrous structure, are best stored in sealed display boxes that protect them from dust and mechanical damage. Avoid locations prone to shocks.