Tridymite

Tridymite is a high temperature polymorph of silica, which typically forms tabular or pseudo-hexagonal crystals in cavities in volcanic rocks.

Particularly of interest to micromount mineral collectors.

Information about Tridymite

Tridymite is a high-temperature polymorph of silica (SiO₂). Other polymorphs of silica include quartz and cristobalite – these are essentially minerals with the same chemical composition but a different crystal structure.

It typically forms tabular, platy, or lath-shaped crystals, often in aggregates, spherulites, or radiating clusters.

Colour is usually colourless, white, pale grey, or light brown, sometimes exhibiting faint yellowish or reddish tones due to impurities. It is transparent to translucent, with a vitreous (glassy) lustre.

 

Uses and History

Tridymite itself has no direct industrial application due to its rarity in large quantities and similarity to quartz. It is primarily of interest to mineralogists and petrologists studying high-temperature volcanic processes, silica polymorphism, and igneous rock formation.

Tridymite was first described from a type locality called Cerro San Cristóbal, in Mexico. It was named from the Greek tridymos, meaning “triplet,” referring to its characteristic intergrowth of three individuals in crystal aggregates.

It has since been identified in many silica-rich volcanic rocks worldwide, particularly in rhyolites and tuffs associated with high-temperature volcanic environments.

 

Mineralogy

Chemistry
Tectosilicite minerals – SiO2.
Colours and Variations

Colourless, white, grey

Streak
Pseudohexagonal plates, also wedge shaped, tabular, in radiating aggregates.
Luster
Vitreous
Transparency
Transparent, translucent
Fracture
Transparent, translucent
Crystal habit
Mohs hardness
7
Fluorescence
Specific Gravity
2.25-2.28
Easiest testing method

Hazards and Warnings

Mineral collectors should wash their hands after handling specimens, to avoid any exposure to potential toxins.

Almost all rocks, minerals (and, frankly, almost all other substances on earth) can produce toxic dust when cutting, which can cause serious respiratory conditions including silicosis. When cutting or polishing rocks, minerals, shells, etc, all work should be done wet to minimise the dust, and a suitable respirator or extraction system should be used.

 

Translations

Arabic:

Hindi:

Portuguese:

Bengali:

Indonesian:

Punjabi:

English:

  • Tridymite

Italian:

Russian:

  • Тридимит

French:

Japanese:

  • 鱗珪石

Spanish:

  • Tridymit

German:

  • Tridymit

Korean:

Thai:

Gujurati:

Mandarin Chinese:

  • 鳞英石

Urdu:

Further Reading / External Links