| Fraipontite | |
|---|---|
 Pockets of minute pearly white fraipontite crystals with green smithsonite from Laurium, Greece (size: 1.4 x 1.0 x 0.9 cm) | |
| General | |
| Category | Phyllosilicate |
| Formula | (Zn,Al)3(Si,Al)2O5(OH)4 |
| IMA symbol | Fpt[1] |
| Strunz classification | 9.ED.15 |
| Crystal system | Monoclinic |
| Crystal class | Domatic (m) (sameH-M symbol) |
| Space group | Cm |
| Unit cell | a = 5.34, b = 9.21 c = 14.12 [Å]; β = 93.2°; Z = 2 |
| Identification | |
| Color | Blueish, yellow white light green |
| Crystal habit | Fibrous to porcelaneous massive |
| Mohs scale hardness | 3.5 – 4 |
| Luster | Silky |
| Streak | White to pale green |
| Diaphaneity | Opaque to translucent |
| Specific gravity | 3.08 – 3.10 |
| Optical properties | Biaxial (-) |
| Refractive index | nα = 1.620 nβ = 1.624 nγ = 1.624 |
| Birefringence | δ = 0.004 |
| 2V angle | Measured: 15° to 20° |
| References | [2][3][4] |
Fraipontite is azincaluminiumsilicate mineral with a formula of(Zn,Al)3(Si,Al)2O5(OH)4.[2][3]
It is a member of thekaolinite-serpentine mineral group and occurs as anoxidation product of zinc deposits. It occurs withsmithsonite,gebhardite,willemite,cerussite andsauconite.[2]
It was first described in 1927 for an occurrence in Vieille Montagne,Verviers,Liège Province,Belgium.[3] It was named forJulien Jean Joseph Fraipont (1857–1910), and Charles de Fraipont, geologists of Liege, Belgium.[4] In addition to thetype locality in Belgium, it has been reported fromTsumeb,Namibia;Laurium,Greece; Swaledale,North Yorkshire,England; the Silver Bill mine,Cochise County, Arizona, the Blanchard Mine,Socorro County, New Mexico and the Mohawk mine,San Bernardino County, California in the US; and from the Ojuela mine, Mapimi,Durango,Mexico.[2]
A synonym of the fraipontite is the zinalsite, which was reported in 1956 for an occurrence inKazakhstan.[5][6]
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