Gemstone profile and identification guide
Fire Agate
Fire agate is a chalcedony variety with iridescent colors caused by thin iron-oxide interference layers.
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Overview
Fire agate is a chalcedony variety with iridescent colors caused by thin iron-oxide interference layers.
Did you know? Cutting fire agate often requires preserving natural botryoidal contour to maximize color play.
Use this profile as a collector reference and educational guide for quick on-page comparison, then validate with the interactive identification system.
Identification
Name: Fire Agate
Scientific classification: Silicate (Chalcedony Quartz Variety)
Hardness: 7 Mohs
Transparency: translucent
Lustre: waxy to vitreous
Crystal system: Trigonal (microcrystalline aggregate)
Primary colour: Brown
Secondary colour: Iridescent Flash Colors
Colour family: Browns
Iridescent flash within brown chalcedony and botryoidal structure are defining characteristics.
Verification Status
Status: verified-core-fields
Reference priority: GIA, Gem-A, Mindat, International Gem Society
Core identity, locality, and physical-property fields reviewed against standard gemological references.
Trade-name entries include treatment/composition disclosures where applicable.
Physical Properties
Hardness category: hard
Hardness value: 7 Mohs
Chemical composition: Silicon dioxide (SiO2) with iron-oxide interference layers
Crystal system: Trigonal (microcrystalline aggregate)
Common locations: Mexico, United States (Arizona, California, New Mexico)
Learn more: Gem-A gemstone education resources.
Colour Variations
Brown chalcedony with iridescent red-green-gold flash from internal iron-oxide layering.
Optical effects: Iridescence
Detailed Gemology
Mineral species: Quartz (chalcedony fire agate variety)
Mineral group: Quartz group
Chemical formula: Silicon dioxide (SiO2) with iron-oxide interference layers
Mohs hardness: 7
Crystal system: Trigonal (microcrystalline aggregate)
Lustre: waxy to vitreous
Transparency: translucent
Streak: White
Cleavage: None
Fracture: Conchoidal
Specific gravity: 2.58-2.64
Refractive index: 1.53-1.54
Optical phenomena: Iridescent interference color
Colour range: Brown host with red/green/gold iridescent flashes
Common inclusions: Iron-oxide films, botryoidal growth structures
Geological environment: Silica and iron-rich volcanic cavity fills
Principal mining regions: Mexico, United States (Arizona, California, New Mexico)
Important commercial sources: Commercial fire agate comes mainly from Mexico and the southwestern United States
Historical significance: A distinctive North American lapidary specialty stone.
Common treatments: Generally untreated; occasional filling in fractured pieces.
Synthetic or imitation forms: Coated glass and imitation composites can mimic iridescence.
Common look-alikes: Iridescent glass, coated chalcedony
Jewellery uses: Used in custom cabochons and collector lapidary work.
Care recommendations: Durable quartz base supports jewellery use; avoid chipping of polished domes and thin relief areas.
Cross-check profile data with GIA Gem Encyclopedia and Mindat entry for Fire Agate.
Formation
Forms in volcanic settings where silica and iron oxide are sequentially deposited in cavities.
Origin
Commercial fire agate comes mainly from Mexico and the southwestern United States
Uses
Best for: Used in custom cabochons and collector lapidary work.
Ideal uses: Cabochons cut to preserve and orient iridescent fire layers.
Care
Durable quartz base supports jewellery use; avoid chipping of polished domes and thin relief areas.
Need another candidate? Use advanced gemstone search or return to the identification guide.
Related gemstones by colour
Related gemstones by hardness
Gemstones from the same mineral family
Commonly confused gemstones
Fire Agate FAQ
How can I identify Fire Agate?
Compare hardness (7 Mohs), crystal system (Trigonal (microcrystalline aggregate)), colour profile, and lustre (waxy to vitreous) with your sample. Then cross-check related gemstones listed above.
What colour range does Fire Agate appear in?
Brown chalcedony with iridescent red-green-gold flash from internal iron-oxide layering.
Where is Fire Agate commonly used?
Cabochons cut to preserve and orient iridescent fire layers.. For maintenance, follow the care guidance in this profile.
Scientific References
GIA: general gemstone identity (reviewed) - Batch 05 factual verification pass.
Gem-A: gemological terminology and testing references (reviewed) - Batch 05 factual verification pass.
Mindat: mineral species and principal localities (reviewed) - Batch 05 factual verification pass.
International Gem Society: gem trade context and treatment overview (reviewed) - Batch 05 factual verification pass.