Paulingite-Na

Chemical formula: (Na<sub>2</sub>,K<sub>2</sub>,Ca,Ba)<sub>5</sub>Al<sub>10</sub>Si<sub>35</sub>O<sub>90</sub>·45H<sub>2</sub>O

A rare zeolite from the paulingite group, forming characteristic, isometric crystals with a vitreous luster, found in gas vesicles in basalts.

## Characteristics Paulingite-Na is a hydrated sodium, potassium, calcium, and barium aluminosilicate, belonging to the zeolite group. It most often forms isometric, spherical crystals, which are in reality complex intergrowths of smaller crystalline forms, resembling rhombic dodecahedra or cubes. Crystals are usually small, rarely exceeding a few millimeters in diameter. Crystal surfaces can be smooth and shiny or matte and slightly rough. ## Physical Properties This mineral is characterized by a hardness of approximately 5 on the Mohs scale. It has a vitreous luster, and its crystals are usually transparent to translucent. The density of paulingite-Na is approximately 2.1 g/cm³. ## Colors and Varieties Paulingite-Na is most often colorless or white. No named color varieties or commercial varieties are distinguished. ## History and Name The mineral's name refers to its chemical composition, in which sodium (Na) is the dominant cation. It is the sodium analog of paulingite-K, which was named in honor of Linus Pauling (1901-1994), an American chemist and crystallographer, Nobel Prize laureate. Paulingite-Na was recognized as a distinct mineral species by the International Mineralogical Association (IMA) in 1997, as a result of the redefinition of the paulingite series. ## Applications Paulingite-Na, like other zeolites, has potential applications as a molecular sieve, catalyst, or in ion exchange processes. However, due to its rarity and small crystal size, it has no industrial significance. It is, however, a valued collector's mineral.

Properties

Mohs hardness
5
Luster
Vitreous
Streak
White
Density
2.08-2.12
Cleavage
Imperfect on {100}
Fracture
Uneven
Transparency
Transparent to translucent
Crystal system
Cubic

Diagnostic features

## Identification Paulingite-Na is identified primarily by its characteristic crystalline form – isometric, often spheroidal or polyhedral aggregates with a vitreous luster. Its occurrence environment is also key – gas vesicles in volcanic rocks, most often basalts. ## Distinguishing from similar minerals It can be confused with other zeolites found in similar conditions, such as chabazite, phillipsite, or analcime. It differs from chabazite by its more complex, spherical crystal form (chabazite forms simple rhombohedra). It differs from analcime in form (analcime forms icositetrahedra) and often lower transparency. Accurate identification requires advanced methods such as X-ray diffraction (XRD) or chemical analysis (EDS). ## Crystal forms Paulingite-Na crystals are isometric. They most often occur as rhombic dodecahedra, often modified, forming aggregates with a spherical or polyhedral appearance. Forms resembling cubes are observed less frequently.

Geological environment

## Genesis Paulingite-Na is a low-temperature hydrothermal mineral. It forms in the late stages of magma crystallization, filling empty spaces (gas vesicles, fissures) in volcanic rocks, mainly in basalts and basaltic tuffs. It crystallizes from solutions rich in silica and alkalis. ## Mineral associations It most often co-occurs with other minerals from the zeolite group, such as phillipsite, chabazite, gmelinite, analcime, as well as with calcite and apophyllite. ## Localities The most important and classic localities for paulingite-Na are in the Czech Republic, in the Ústí nad Labem region (e.g., in the towns of Dobrná, Radejčín, Suletice). This mineral has also been found in basalts in Vogelsberg in Hesse (Germany) and in several localities in Oregon, USA (e.g., Ritter, Rock Island Dam).

Rarity

Rare

For collectors

## Quality Criteria The most valued by collectors are specimens with well-formed, sharp, and shiny crystals of significant size (for this mineral), exceeding 2-3 mm. Specimens where colorless or white paulingite crystals contrast with the dark matrix rock (basalt) are also highly rated. Aesthetic composition and the absence of damage to delicate crystals are important. ## Popular Localities The most famous collector's specimens, considered the best in the world, come from classic localities in the Czech Republic, especially from quarries around Ústí nad Labem. Specimens from these localities serve as a benchmark for this mineral.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush to remove dust. Brief rinsing in distilled water is permissible, after which the specimen should be immediately and thoroughly dried. Due to its complex, microporous structure, prolonged contact with water is not recommended. ## What to avoid Avoid contact with acids and other chemicals that can damage the delicate aluminosilicate structure. The mineral is sensitive to heating, which leads to irreversible loss of structural water (dehydration) and crystal destruction. It should not be cleaned in ultrasonic cleaners. Protect it from prolonged exposure to moisture. ## Storage Paulingite-Na specimens are best stored in closed, stable containers (e.g., membrane boxes or display cases) to protect them from dust, mechanical damage, and sudden changes in humidity. Fragile crystals require careful handling.

Sources

Read more