Priscillagrewite-(Y)

Chemical formula: YCa₂Zr⁴⁺₂Al₃O₁₂

Priscillagrewite-(Y) is a very rare mineral from the garnet supergroup, distinguished by the presence of yttrium and zirconium in its chemical composition.

## Characteristics Priscillagrewite-(Y) is a mineral belonging to the garnet supergroup. It occurs as very small, isolated grains, usually not exceeding 20 micrometers in size. Due to its microscopic size, its visual characteristics are difficult to assess without specialized equipment. The observed crystals are transparent and have a delicate, pale yellow hue. ## Physical Properties The mineral is characterized by a hardness of 7-7.5 on the Mohs scale, which is typical for garnets. Its density is 4.48 g/cm³. The crystals are transparent and exhibit a vitreous luster. Due to the size of the grains, features such as cleavage or fracture have not been determined. ## Colors and Varieties The only known color of this mineral is pale yellow. No varieties have been distinguished. ## History and Name The mineral is named in honor of Priscilla Grew, wife of American mineralogist Edward S. Grew, for her contributions to the study of metamorphic minerals. The "(Y)" suffix refers to the dominant rare earth element in its composition – yttrium. The mineral was approved by the International Mineralogical Association (IMA) in 2021. ## Applications Priscillagrewite-(Y) has no industrial applications. Its significance is purely scientific and collectible, as a unique member of the garnet supergroup.

Properties

Mohs hardness
7-7.5
Luster
Vitreous
Density
4.48
Transparency
Transparent
Crystal system
Isometric

Diagnostic features

## Identification Identification of priscillagrewite-(Y) is impossible without advanced analytical techniques, such as electron microprobe analysis (EMPA) or Raman spectroscopy. It occurs as microscopic, pale yellow grains embedded in the host rock (marble). Its high hardness and belonging to the garnets are clues, but do not allow for certain identification. ## Distinguishing from Similar Minerals It can be confused with other zirconium-bearing garnets, such as kerimasite or kimzeyite. Definitive differentiation requires chemical analysis, particularly confirmation of the dominance of yttrium and calcium at specific positions in the crystal structure. ## Crystal Forms The mineral forms very small, isolated, anhedral (irregular) grains.

Geological environment

## Genesis Priscillagrewite-(Y) forms under conditions of high-grade contact metamorphism, in contact zones between basaltic melts and carbonate sediments. It forms at temperatures exceeding 800°C. It occurs in marbles formed from the alteration of rocks of the Mottled Zone formation. ## Mineral Associations This mineral co-occurs with other high-temperature minerals, such as calcite, gehlenite, larnite, rankinite, walstromite, and also other garnets, e.g., kerimasite. ## Localities The only confirmed locality of priscillagrewite-(Y) in the world is its type locality – the Daba marble quarry in the Daba-Siwaqa complex in Jordan.

Rarity

Extremely rare

For collectors

## Quality Criteria As a microscopic mineral, priscillagrewite-(Y) is not evaluated by typical collector criteria such as size or crystal form. The value of a specimen lies solely in the confirmed presence of this extremely rare mineral in the host rock. The most valuable samples are those with the largest number of grains, well-documented analytically. ## Popular Localities The only source of specimens is the Daba quarry in Jordan. Material from this locality is extremely difficult to obtain and appears on the collector's market sporadically.

Care and storage

## Cleaning Due to the extremely small size of the crystals and their embedding in the host rock, specimens do not require and should not be subjected to cleaning. Any attempt at mechanical or chemical cleaning would destroy the specimen. ## What to Avoid All chemicals, ultrasound, and sudden temperature changes should be avoided. Specimens should be protected from abrasion and mechanical damage. ## Storage Specimens containing priscillagrewite-(Y) should be stored under stable conditions, preferably in specialized "micromount" boxes, which protect them from dust and physical damage. Exposure to moisture and contaminants should be avoided.

External references

Sources

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