Eakerite
Chemical formula: Ca<sub>2</sub>Sn<sup>4+</sup>Al<sub>2</sub>Si<sub>6</sub>O<sub>18</sub>(OH)<sub>2</sub>·2H<sub>2</sub>O
Eakerite is a very rare tin and calcium silicate, forming colorless or white, acicular crystals in pegmatite vugs.
Properties
- Mohs hardness
- 4
- Luster
- Vitreous
- Streak
- White
- Density
- 2.93
- Cleavage
- Perfect on {100}
- Fracture
- Uneven
- Transparency
- Transparent to Translucent
- Crystal system
- Monoclinic
Diagnostic features
## Identification Characteristic features of eakerite include its crystal forms – slender, acicular crystals often grouped in radial aggregates. Its occurrence is limited to vugs in lithium pegmatites. Vitreous luster and white or colorless appearance are also helpful in identification. However, definitive confirmation requires advanced analytical methods, such as X-ray diffraction (XRD). ## Distinguishing from Similar Minerals Eakerite can be confused with other white, acicular minerals found in pegmatites, such as natrolite, scolecite, or bavenite. It is distinguished from zeolites (natrolite, scolecite) by the presence of tin in its chemical composition, which requires specialized analysis. The mineralogical context, especially co-occurrence with other minerals from the Foote mine, is a key indicator. ## Crystal Forms Eakerite crystals are elongated, prismatic to acicular. They typically form fan-shaped, radial, or chaotically arranged groups and aggregates within small rock vugs (miarolitic cavities).
Geological environment
## Genesis Eakerite is a hydrothermal mineral, crystallizing in the late stages of the formation of complex, lithium-rich granitic pegmatites. It forms in miarolitic cavities, where rare minerals precipitate from post-magmatic solutions. ## Mineral Associations This mineral co-occurs with other minerals typical of pegmatites from the Foote mine. Its most common associations include albite, quartz, muscovite, spodumene, bikitaite, eucryptite, bavenite, and various phosphates, such as vivianite or fairfieldite. ## Localities The most important and historical locality for eakerite, from which the world's best specimens originate, is the Foote Lithium Co. mine in Kings Mountain, Cleveland County (North Carolina, USA). This is its type locality. Outside the USA, its presence has also been reported in the Viitaniemi pegmatite in Finland.
Rarity
Very rare
For collectors
## Quality Criteria The most highly valued eakerite specimens are those with well-formed, sharp, and lustrous crystals, forming aesthetic, radial groups. Specimens on matrix, especially in contrast with other minerals, are more desirable than single, loose crystals. The size of the crystals and entire aggregates also significantly affects value, as does the absence of damage. ## Popular Localities The vast majority of the best collectible specimens come from one place in the world – the historic Foote mine in North Carolina, USA. Specimens from this locality are classic and the standard for this mineral.
Care and storage
## Cleaning Eakerite specimens should be cleaned very carefully, using a soft brush and distilled water to remove dust and loose contaminants. Due to its brittleness and perfect cleavage, strong rubbing should be avoided. Ultrasonic cleaners are absolutely not recommended, as they can cause crystals to disintegrate. ## What to Avoid The mineral is sensitive to shocks and impacts, which can cause fracturing along cleavage planes. Contact with harder minerals should be avoided to prevent scratching. As a hydrated mineral, it may be sensitive to high temperatures, which can lead to dehydration and structural damage. Contact with acids and strong chemicals should also be avoided. ## Storage Collectible eakerite specimens are best stored in separate, padded boxes (micromount type) to protect them from mechanical damage and contact with other minerals. They should be protected from dust and sudden temperature changes.