Hydroxymcglassonite-(K)

Chemical formula: KSr<sub>4</sub>Si<sub>8</sub>O<sub>20</sub>(OH)·8H<sub>2</sub>O

Hydroxymcglassonite-(K) is a very rare potassium and strontium silicate, forming colorless, bladed crystals with a pearly luster.

## Characteristics Hydroxymcglassonite-(K) is a hydrated layered silicate from the gismondine group. This mineral forms very small, colorless, bladed or tabular crystals, usually not exceeding 0.5 mm in length. The crystals are transparent and exhibit a pearly luster on cleavage surfaces and a vitreous luster on other faces. They typically occur as small, radial aggregates or tangled masses. ## Physical Properties The crystals are flexible and can be bent. The Mohs hardness is approximately 2. The mineral's density is 2.53 g/cm³. The luster is pearly to vitreous, and the streak is white. It is transparent. ## History and Name The mineral's name refers to its chemical composition – the dominance of the hydroxyl (OH) group, potassium (K), and its relation to mcglassonite. It was approved as a new mineral by the International Mineralogical Association (IMA) in 2009 (IMA2009-068). It was described by D. I. Belakovskiy, N. V. Chukanov, Yu. A. Pautov, and others in 2011, based on material from the Murun Massif in Russia.

Properties

Mohs hardness
2
Luster
Pearly
Streak
White
Density
2.53
Cleavage
Perfect on {001}
Fracture
Uneven
Transparency
Transparent
Crystal system
Monoclinic

Diagnostic features

## Identification Identification is practically only possible using advanced analytical methods, such as infrared spectroscopy (IR) and chemical analysis (EDS/WDS). Visually, it is indistinguishable from many other white or colorless secondary minerals. ## Differentiation from Similar Minerals It can be confused with other zeolites or related silicates, such as reyerite, truscottite, or mcglassonite. Definitive differentiation requires specialized laboratory equipment. ## Crystal Forms It forms thin, bladed or tabular crystals, elongated along the [100] axis and flattened parallel to {001}. They occur as radial or tangled aggregates.

Geological environment

## Genesis It is a hydrothermal mineral. It forms in the late stages of crystallization in pegmatite veins or in altered alkaline rocks. At the type locality (Murun Massif), it occurs in aegirine-calcite-microcline pegmatites cutting fenites. ## Mineral Associations At the type locality, it co-occurs with aegirine, microcline, quartz, pectolite, tokkoite, tinaksite, fluorite, frankamenite, and daqingshanite-(Ce). ## Localities The only confirmed occurrence of this mineral in the world is the Murun Massif (Tausonitovaya Gorka), on the border of the Irkutsk Oblast and Yakutia in Russia.

Rarity

Extremely rare

For collectors

## Quality Criteria Due to its extreme rarity, every analytically confirmed specimen is extremely valuable for specialized collectors of rare and systematic minerals. The most highly prized would be rich, well-formed crystal aggregates on a contrasting matrix, but such specimens are practically unheard of.

Care and storage

## Cleaning Due to its extreme rarity and delicacy, specimens should not be cleaned mechanically or chemically. If necessary, compressed air (from a safe distance) can be used to remove dust. ## What to Avoid Avoid contact with water, chemicals, ultrasound, and sudden temperature changes. The mineral is very soft and brittle, susceptible to mechanical damage. ## Storage Specimens should be stored exclusively in specialized "micromount" boxes, protecting them from dust, humidity, and vibrations. Do not expose them to direct light.

Sources

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