Hydromagnesite
A variety of Minerals
What is Hydromagnesite?
Hydromagnesite is formed when certain magnesium-containing minerals are weathered down. The mineral not particularly common, and it's most often found in caves, so most people don't have much direct contact with it. Because it gives off water and carbon dioxide when it decomposes, hydromagnesite is used in flame retardants.
Uses & Applications
Hydromagnesite is commonly used in industry for its fire retardant properties, and it is incorporated into many plastic products as a fire proofing agent. Research is currently ongoing to determine if hydromagnesite would also be a good flame retardant in electric devices.
Market Value Factors
Pricing varies for every rock and mineral, so use these universal factors to gauge Hydromagnesite 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.
Hydromagnesite Localities Map
See where Hydromagnesite is found with a localities map, collecting zones, and geology context. Generate a sample map preview below.
Key Characteristics
Composition of Hydromagnesite
Hydromagnesite thermally decomposes in three stages releasing water and carbon dioxide. The first stage starting at about 220 °C, is the release of the four molecules of water of crystallisation. This is followed at about 330 °C by the decomposition of the hydroxide ion to a further molecule of water. Finally, at about 350 °C carbon dioxide begins to be released. The release of the carbon dioxide can be further broken down into two stages depending on the rate of heating.
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Quick Facts
Physical Properties
- Color
- Colourless to white, colourless in transmitted light
- Hardness (Mohs)
- 3.5
- Density
- 2.236 g/cm³
- Streak
- White
- Luster
- Pearly, Vitreous, Silky, Dull
- Crystal System
- Monoclinic
Chemical Properties
- Chemical Formula
- Mg5(CO3)4(OH)2 · 4H2O
- Elements
- C, H, Mg, O
Also Known As
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Hydromagnesite FAQs
How do I identify Hydromagnesite?
Hydromagnesite can be identified by its hardness of 3.5 on the Mohs scale, Colourless to white color, Pearly, Vitreous, Silky, Dull luster, Monoclinic crystal system. Look for these key characteristics when examining specimens.
What color is Hydromagnesite?
Hydromagnesite typically appears in Colourless to white, colourless in transmitted light. Color can vary depending on impurities and formation conditions.
How hard is Hydromagnesite?
Hydromagnesite has a hardness of 3.5 on the Mohs scale. This gives it moderate hardness.
What is the composition of hydromagnesite of Hydromagnesite?
Hydromagnesite thermally decomposes in three stages releasing water and carbon dioxide. The first stage starting at about 220 °C, is the release of the four molecules of water of crystallisation. This is followed at about 330 °C by the decomposition of the hydroxide ion to a further molecule of water. Finally, at about 350 °C carbon dioxide begins to be released. The release of the carbon dioxide can be further broken down into two stages depending on the rate of heating.
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