Hyalite
Variety SiO2·nH2O
Also called Water opal and Müller's glass
Take care.
- Sensitive to heat: Keep it away from heat and sudden changes of temperature, including hot lights and ultrasonic cleaners.
About it
Water-clear, glassy opal in rounded crusts and droplets. Traces of uranium make it glow vivid green under UV; Zacatecas, Mexico, and Valeč, Czech Republic, are well known.
- Type
- Variety
- Group
- Opal variety
- Formula
- SiO2·nH2O
- Hardness (Mohs)
- 5.5–6.5
- Specific gravity
- 1.98–2.25
- Streak
- white
- Lustre
- vitreous (glassy)
- Crystal system
- Amorphous (no crystal structure)
- Colours
- colourless, pale yellow, glassy
- Transparency
- transparent
- Cleavage and fracture
- none; conchoidal fracture
- Under UV light
- bright green under UV, strongest under shortwave
Typical values: real specimens vary. For more, see mindat.org.