Montana Moss Agate
A variety of Chalcedony
What is Montana Moss Agate?
Montana Moss Agate is a Moss Agate found exclusively in the alluvial gravels of the Yellowstone River (Montana, USA). This semi-precious stone is mostly yellow or white, with prominent, dark, tree-like or moss-like markings. The attractive and unusual appearance is a result of volcanic activities and lava flows in Yellowstone National Park.
Optical Properties
- Refractive Index
- 1.530-1.543
- Birefringence
- 0.003-0.009
- Pleochroism
- None
- Optical Character
- Biaxial positive
- Dispersion
- 0.013
Discover Values
This stone excels in beauty.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Montana Moss Agate before comparing listings or appraisals.
Size & Weight
Larger, intact specimens usually command higher prices.
Rarity & Demand
Scarce material or popular varieties sell at a premium.
Condition & Finish
Chips, repairs, and heavy wear lower value; clean prep helps.
Treatment & Provenance
Untreated specimens with documented locality are prized.
Montana Moss Agate Localities Map
See where Montana Moss Agate is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Formation of Montana Moss Agate
It was originally formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity.
Health & Safety Information
- ⚠️Montana Moss Agate in powdered form can be toxic due to its Crystalline Silica content.
- ⚠️Quartz, silica, crystalline silica and flint are non-toxic materials, but very fine dust containing quartz, known as respirable crystalline silicon (RCS), can cause serious and fatal lung disease. Lapidaries should exercise caution when cutting silica.
- ⚠️Montana Moss Agate is typically non-toxic unless it's in powder form. Long-term exposure to finely ground powder may lead to silicosis. Therefore, when cutting or polishing montana Moss Agate, be sure to wear a dust mask to avoid inhaling its dust.
Quick Facts
Physical Properties
- Color
- Gray, white, brown, black, red, orange, yellow
- Hardness (Mohs)
- 6.5 - 7
- Density
- 2.55 - 2.7 g/cm³
- Streak
- Green
- Luster
- Waxy, Vitreous
- Crystal System
- Trigonal
Chemical Properties
- Chemical Formula
- SiO2
- Elements
- Si, O
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Montana Moss Agate FAQs
How do I identify Montana Moss Agate?
Montana Moss Agate can be identified by its hardness of 6.5 - 7 on the Mohs scale, Gray color, Waxy, Vitreous luster, Trigonal crystal system. Look for these key characteristics when examining specimens.
What color is Montana Moss Agate?
Montana Moss Agate typically appears in Gray, white, brown, black, red, orange, yellow. Color can vary depending on impurities and formation conditions.
How hard is Montana Moss Agate?
Montana Moss Agate has a hardness of 6.5 - 7 on the Mohs scale. This gives it moderate hardness.
What is the formation of montana moss agate of Montana Moss Agate?
It was originally formed in the Yellowstone National Park area of Wyoming as a result of volcanic activity.