Hyalite is a transparent form of opal with a glassy

lustre Lustre or Luster may refer to: Places * Luster, Norway, a municipality in Vestlandet, Norway ** Luster (village), a village in the municipality of Luster * Lustre, Montana, an unincorporated community in the United States Entertainment * ' ...

. It may exhibit an internal play of colors if natural inclusions are present. It is also called Muller's glass, water opal, and jalite. Müller's glass is named after its discoverer, Franz-Joseph Müller von Reichenstein.

Properties

Hyalite's

Mohs hardness The Mohs scale of mineral hardness () is a qualitative ordinal scale, from 1 to 10, characterizing scratch resistance of various minerals through the ability of harder material to scratch softer material. The scale was introduced in 1812 by ...

is 5.5 to 6 and has a specific gravity of 1.9 - 2.1. It has no planes of cleavage but fractures conchoidally, is clear or translucent and has a globular structure. Its luster is vitreous and its streak is white. Hyalite is an

amorphous In condensed matter physics and materials science, an amorphous solid (or non-crystalline solid, glassy solid) is a solid that lacks the long-range order that is characteristic of a crystal. Etymology The term comes from the Greek ''a'' ("wit ...

form of silica (SiO₂) formed as a volcanic sublimate in volcanic or pegmatic rock and is therefore considered a mineraloid. It contains 3 - 8% water, either as a

silanol A silanol is a functional group in silicon chemistry with the connectivity Si–O–H. It is related to the hydroxy functional group (C–O–H) found in all alcohols. Silanols are often invoked as intermediates in organosilicon ch ...

group or in molecular form.

Uses

Opalescent hyalite is used in jewellery, and well-formed samples are of interest to collectors due to their unusual appearance, mode of formation and relative rarity. It is sometimes mistaken for resin opal or

silica glass Fused quartz, fused silica or quartz glass is a glass consisting of almost pure silica (silicon dioxide, SiO2) in amorphous (non-crystalline) form. This differs from all other commercial glasses in which other ingredients are added which change ...

since they both may appear clear and globular, but it can be identified under ultraviolet light due to its bright green fluorescence.

External links

Mindat dataExplanation from Fluorescent Mineral Society
Opals {{mineral-stub