Fire opal
Variety SiO2·nH2O
Also called Mexican opal
Take care.
- Sensitive to heat: Keep it away from heat and sudden changes of temperature, including hot lights and ultrasonic cleaners.
About it
Transparent yellow to red opal, prized for its body colour whether or not it shows play-of-colour. The classic source is Querétaro, Mexico; not to be confused with fire agate.
- 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), resinous
- Crystal system
- Amorphous (no crystal structure)
- Colours
- yellow, orange, red, brownish red
- Transparency
- transparent, translucent
- Cleavage and fracture
- none; conchoidal fracture
Typical values: real specimens vary. For more, see mindat.org.