Glass-(Sm)

A natural, amorphous calcium and rare-earth aluminosilicate with dominant samarium, found in Israel.

## Characteristics The substance known as Glass-(Sm) is a natural, amorphous glass, not a formally recognized mineral. It occurs as very small, irregular fragments up to 1 mm in size. Specimens are transparent and characterized by a pale yellowish-green color. Due to its amorphous (non-crystalline) nature, it does not form crystals. ## Physical Properties As a glass, this material exhibits a typical vitreous luster and conchoidal fracture. It is transparent. It does not show cleavage. Its hardness and density have not been thoroughly studied and described in the literature. ## Colors and Varieties The only known color is a uniform, pale yellowish-green. No color varieties or commercial varieties are distinguished. ## History and Name The name "Glass-(Sm)" is an informal term used in collecting and scientific circles to describe this specific substance. It is not a name approved by the International Mineralogical Association (IMA). The "(Sm)" in the name refers to the dominant rare-earth element in its chemical composition – samarium. This material was identified within the unique geological Hatrurim Formation in Israel. ## Applications Due to its extreme rarity and microscopic size, Glass-(Sm) has no industrial applications. It is solely an object of scientific interest and a rarity in advanced micromineral collections.

Properties

Luster: Vitreous
Cleavage: None
Fracture: Conchoidal
Transparency: Transparent

Diagnostic features

## Identification Identification is based on its physical properties: vitreous luster, conchoidal fracture, pale yellowish-green color, and lack of crystalline structure. However, a key indicator is its origin from the Hatrurim Formation in Israel. Final confirmation of identity requires advanced chemical analysis (e.g., EDS) to demonstrate the dominance of samarium among rare-earth elements. ## Differentiation from Similar Materials It can be confused with other natural glasses (e.g., fragments of tektites, fulgurites) or artificial glass. The main differentiating factor is its unique chemical composition with a high content of rare-earth elements and the specific occurrence environment (pyrometamorphism of the Hatrurim Formation). Other minerals from this locality will have a crystalline structure. ## Crystal Forms As an amorphous substance, Glass-(Sm) does not form crystals. It occurs exclusively as irregular, rounded, or angular fragments.

Geological environment

## Genesis Glass-(Sm) is a product of pyrometamorphism – a rare natural process of combustion and melting of sedimentary rocks at high temperatures and low pressures. The rapid cooling of the resulting melt prevented crystallization, leading to the formation of glass. This process is characteristic of the Hatrurim Formation in Israel. ## Mineral Associations It co-occurs with other rare minerals formed under pyrometamorphic conditions, such as larnite, spurrite, brownmillerite, and other, often unnamed mineral phases typical of this formation. ## Localities The only confirmed locality in the world is the Halamish Wadi (Nahal Halamish) area within the Hatrurim Formation in the Negev Desert, Israel.

Rarity

Extremely rare

For collectors

## Quality Criteria For microscopic material, the primary criterion for value is scientific confirmation of its identity through chemical analysis. The size of the fragment, its purity (lack of inclusions), and the intensity of its color are secondary factors. Specimens intergrown with other rare, well-formed minerals from this locality are highly prized. ## Popular Localities Specimens originate exclusively from one location in the world – the Hatrurim Formation in Israel, which makes them extremely sought after by specialized collectors of microminerals and rare minerals.

Care and storage

## Cleaning Specimens should be cleaned very carefully, using a soft brush and distilled water. Due to their microscopic size and potential fragility, ultrasonic cleaners are not recommended. ## What to Avoid Avoid contact with strong chemicals, especially hydrofluoric acid, which etches silicates. Abrupt temperature changes can lead to cracking. The material is stable in light. ## Storage As a micromaterial, it requires storage in a specialized "micromount" box, with an appropriate label, to prevent loss. It should be protected from dust and mechanical damage.

Sources

IMA Mineral List (CNMNC)