Agatized algae forms when silica-rich fluids permeate ancient algal mats, preserving the delicate layered structures within chalcedony. Look for characteristic wavy, concentric banding or distinct 'biscuit' patterns that reveal the organic history of the specimen. It is highly sought after by lapidaries for its unique patterns when sliced and polished.
Is this agatized algae?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch agatized algae with a known reference. Agatized Algae sits at Mohs 6.5-7 — softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Agatized Algae leaves a white streak.
- 3Read the lusterHold the specimen under a strong light. Agatized Algae typically shows a waxy luster.
- 4Match the color rangeCompare against the expected color range: brown, red, tan, gray, white, yellow.
- 5Look at form & habitTypical habit: massive.
Often confused with
Agatized Algae vs. its common look-alikes — and how to tell them apart in the field.
Often found alongside agatized algae
Minerals reported to co-occur with agatized algae. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- SiO₂
- Mohs hardness
- 6.5-7
- Density
- 2.6-2.7 g/cm³
- Streak
- White
- Luster
- Waxy
- Transparency
- Translucent
- Crystal habit
- Massive
- Cleavage
- None
- Rarity
- Common
- Uses
- Lapidary, Collector
- Host rock
- Sedimentary Strata
- Typical price
- $5-50 for small slabs or polished specimens
Where rockhounds find agatized algae
1 mapped spotsClassic worldwide localities
- Wyoming, USA
- Montana, USA
- Utah, USA
- Australia
- Mexico
Field-hunting tip
Look in sedimentary strata country — that is the host setting where agatized algae typically forms. If you start seeing quartz, calcite, chalcedony in float, you are in the right ground. Field specimens usually show a massive habit, so train your eye for that shape before scanning the outcrop. In the U.S., the densest reported localities are in Oklahoma — start trip planning there.
Common questions
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Find agatized algae on the map
RockHoundR shows mapped rockhounding spots, access rules, and lets you log every find.
