Celadonite
Celadonite is a mica group mineral, a phyllosilicate of potassium, iron in both oxidation states, aluminium and hydroxide with formula K(Mg,Fe2+
)(Fe3+
,Al)[Si
4O
10](OH)
2.
| Celadonite | |
|---|---|
 Green crystals of heulandite which owe their green colour to many tiny inclusions of celadonite | |
| General | |
| Category | Micas Phyllosilicate |
| Formula (repeating unit) | K(Mg,Fe2+ )(Fe3+ ,Al)[Si 4O 10](OH) 2 |
| Crystal system | Monoclinic |
| Crystal class | Spheroidal (2) (same H-M symbol) |
| Space group | C2 |
| Identification | |
| Color | Blue-green to olive to applegreen |
| Cleavage | perfect on {001} |
| Tenacity | Fragile |
| Mohs scale hardness | 2 |
| Luster | Waxy, dull, earthy |
| Diaphaneity | Translucent |
| Specific gravity | 2.95 - 3.05 |
| Density | 2.95 - 3.05 |
| Optical properties | Biaxial (-) |
| Pleochroism | Visible |
| 2V angle | 5°- 8° |
| Common impurities | Mn, Na, Ca |
| Other characteristics |  Radioactive 9.11% (K) |
| References | [1][2][3] |
It crystallizes in the monoclinic system and usually forms massive aggregates of prismatic crystallites or in dull clay masses. It is soft with a Mohs hardness of 2 and a specific gravity of 3. Typically occurs as dull gray-green to bluish green masses. It forms vesicle fillings and linings in altered basaltic lavas.
It was first described in 1847 on Monte Baldo, near Verona, Italy. The name is from the French celadon, for sea-green. It is one of two minerals, along with glauconite, used in making the pigment known as green earth.
Common impurities are manganese, calcium and sodium (previously known as natrium).
References
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