Lizardite
Mg3Si2O5(OH)4 [CNMNC approved formula]
Named from the locality: The Lizard, Cornwall, England.
| IMA status : | Valid species (Pre-IMA 1956) Grandfathered |
| CLASSIFICATION | |
| Dana (8th edition) : |
71.01.02b.02 |
| (71) Phyllosilicate Sheets of Six-Membered Rings | |
| (71.01) with 1:1 layers | |
| (71.01.02b) Serpentine group (Lizardite subgroup) | |
| Nickel-Strunz (10th edition) : |
09.ED.15 |
| (09) Silicates | |
| (09.E) Phyllosilicates | |
| (09.ED) Phyllosilicates with kaolinite layers composed of tetrahedral and octahedral nets | |
| Crystal system: | Trigonal System |
| Point group (H-M): | 3m — ditrigonal-pyramidal |
| Unit cell: | a = 5.325 Ǻ, c = 7.259 Ǻ |
| Crystal Habit: | Massive, fine- to coarse-grained, compact; small scales |
| Color: | Green, green-blue, white |
| Diaphaneity: | Translucent |
| Luster: | Waxy |
| Hardness (Mohs): | 2.5 |
| Measured Density: | 2.55 to 2.60 g/cm3 |
| Cleavage: | 1; {0001} perfect |
| Tenacity: | Crystals are easily bent |
| Polymorphism and Series: | Polymorphous with antigorite, clinochrysotile, orthochrysotile, and parachrysotile. Forms a series with nepouite. |
| Geologic Setting: | Typically a product of retrograde metamorphism, replacing olivine, orthopyroxene, or other minerals in ultramafic igneous rocks. |
| Mineral Association: | Chrysotile, brucite, magnetite |
| Synonyms/varieties: | Green variety bastite, Al-lizardite, Nickeloan Lizardite |
| Comments: | Polytypes :1A, 6A, 2H. |
Green variety bastite partly after orthopyroxene in harzburgite matrixOrigin: Baste, south of Bad Harzburg, Harz, Germany
Sample size: 5 x 11 cm
Photo: Diederik Visser