Nagelschmidtite
Chemical formula: Ca₇(SiO₄)₂(PO₄)₂
Nagelschmidtite is a rare calcium silicophosphate, occurring in microscopic grains in metamorphic rocks and some slags.
Properties
- Mohs hardness
- 5
- Color
- yellowish white
- Luster
- Vitreous
- Streak
- white
- Density
- 0
- Cleavage
- None
- Fracture
- Uneven
- Transparency
- Transparent
- Crystal system
- Hexagonal
Diagnostic features
## Identification Identification of nagelschmidtite is possible only through advanced analytical methods, such as X-ray diffraction (XRD) or X-ray microanalysis (EDS/WDS), due to its microscopic size and occurrence in complex parageneses. Visual identification in the field or even in a collection is impossible. ## Distinguishing from similar minerals It can be confused with many other colorless minerals found in the Hatrurim Formation, such as larnite, brownmillerite, or jasmundite. Differentiation requires specialized analysis of chemical composition and crystal structure. ## Crystal forms Nagelschmidtite forms very small, anhedral (irregular) or rounded grains, usually less than 100 micrometers in size. Poorly formed, tabular crystals are rarely observed.
Geological environment
## Genesis Nagelschmidtite is a product of pyrometamorphism (contact metamorphism at extremely high temperatures) of carbonate rocks. It forms under conditions of low pressure and temperatures reaching 800-900°C. It is a characteristic mineral of the Hatrurim Formation (also known as the "Mottled Zone") in the Middle East. ## Mineral associations This mineral co-occurs with other high-temperature calcium-silicate minerals, such as larnite, brownmillerite, jasmundite, mayenite, ye'elimite, as well as calcite and fluorellestadite. ## Localities The most important and classic occurrences of nagelschmidtite are found in Israel and the Palestinian territories, within the Hatrurim Formation (e.g., Hatrurim, Ma’ale Adummim). It has also been identified in Jordan and in coal dump combustion products, for example, in Kopeysk in the Southern Urals, Russia.
Rarity
Very rare
For collectors
## Quality criteria As a micromineral, the collector's value of nagelschmidtite primarily depends on the confirmation of its identity through analysis. Specimens where the mineral grains are relatively "large" (visible under a stereomicroscope) and occur alongside other rare minerals from the same paragenesis are more desirable. The abundance of grains on the matrix also increases the specimen's value. ## Popular localities The most prized specimens by collectors come from the type locality in the Hatrurim Formation in Israel.
Care and storage
## Cleaning Specimens containing nagelschmidtite, typically microminerals on a rock matrix, do not require cleaning. If necessary, compressed air can be used to remove dust. Avoid contact with water and chemicals. ## What to avoid Avoid all acids, which can react with phosphates and silicates. Due to the small size of the crystals, specimens are sensitive to mechanical damage and abrasion. ## Storage It is recommended to store specimens in specialized micromount boxes, which protect them from dust, moisture, and mechanical damage. Avoid exposure to extreme temperature changes.