Cloud Agate Identification Guide
Identify cloud agate by its soft, hazy white-and-gray cloud-like inclusions within translucent chalcedony, and tell it from moss and dendritic agate.
Read the full Cloud Agate encyclopedia entry →
What Cloud Agate Looks Like
Cloud agate is a translucent chalcedony (microcrystalline quartz) agate marked by diffuse, soft-edged white or gray patches that resemble clouds, smoke, or mist suspended inside the stone. Unlike sharply banded agate, the markings are blurry and gradational. The base is usually pale gray, bluish, or colorless and translucent, with a waxy to vitreous luster. Some pieces combine cloudy zones with faint fortification banding.
Step-by-Step Field ID Checklist
- Backlight the stone. Hold it to a light: cloud agate glows translucently and reveals the internal hazy clouds.
- Examine the markings. Look for soft, fuzzy, gradational white/gray clouds rather than crisp bands or branching threads.
- Check luster on a broken face. A waxy-to-glassy conchoidal surface indicates chalcedony.
- Test hardness. It scratches glass easily (Mohs ~6.5–7).
- Feel the surface. Polished pieces are smooth and slightly cool; agate takes a high polish.
- Look for banding. Faint concentric fortification bands confirm agate rather than plain chalcedony.
Key Diagnostic Tests
- Hardness: 6.5–7 (quartz family). Scratches glass; not scratched by a knife.
- Streak: White.
- Fracture: Conchoidal, no cleavage.
- Density: ~2.6 g/cm³.
- No acid reaction, non-magnetic, translucent.
- Diagnostic feature: Diffuse cloud-like internal inclusions in translucent chalcedony.
Common Look-Alikes and How to Tell Them Apart
- Moss agate: Moss agate has green, brown, or black filaments resembling moss or plants (mineral dendrites/inclusions). Cloud agate's markings are soft white/gray clouds, not branching filaments.
- Dendritic agate: Shows tree- or fern-like black/brown branching patterns with sharp edges; cloud agate is fuzzy and lacks branching dendrites.
- Banded/fortification agate: Has crisp concentric color bands; cloud agate's haze is diffuse.
- Chalcedony (plain): Uniformly translucent with no internal clouds; cloud agate specifically has the misty inclusions.
- Common opal: Softer (5.5–6.5), often lacks chalcedony's waxy fracture and may be lighter.
Where It Is Found
Cloud agate, like other agates, forms in gas cavities and fractures of volcanic rocks (basalt, rhyolite) where silica-rich solutions deposit chalcedony. It is found in agate-bearing regions worldwide, including the western United States (Oregon, Montana, Wyoming), Mexico, Brazil, and India. Hunt in basalt flows, river gravels, and weathered volcanic terrains.
Frequently asked questions
What does cloud agate look like?
It is a translucent gray, bluish, or colorless chalcedony agate containing soft, diffuse white or gray patches that look like clouds or smoke suspended inside the stone.
How can you tell if it's real cloud agate?
Backlight it: genuine cloud agate is translucent with hazy internal clouds, has hardness 6.5–7 (scratches glass), shows waxy conchoidal fracture, and may have faint fortification banding.
Cloud agate vs moss agate — what's the difference?
Moss agate has green, brown, or black branching, moss-like mineral filaments. Cloud agate's markings are soft, fuzzy white or gray clouds without any plant-like branching.
Is cloud agate the same as dendritic agate?
No. Dendritic agate has sharp tree- or fern-like dark branching patterns, while cloud agate shows diffuse, blurry cloud-like inclusions.
Cloud Agate identified by the community
Recent Cloud Agate specimens identified with Rock Identifier.
