| Fraipontite | |
| Category: | Phyllosilicate |
| Imasymbol: | Fpt[1] |
| Strunz: | 9.ED.15 |
| System: | Monoclinic |
| Class: | Domatic (m) (same H-M symbol) |
| Symmetry: | Cm |
| Unit Cell: | a = 5.34, b = 9.21 c = 14.12 [Å]; β = 93.2°; Z = 2 |
| Color: | Blueish, yellow white light green |
| Habit: | Fibrous to porcelaneous massive |
| Mohs: | 3.5 – 4 |
| Luster: | Silky |
| Streak: | White to pale green |
| Diaphaneity: | Opaque to translucent |
| Gravity: | 3.08 – 3.10 |
| Opticalprop: | Biaxial (-) |
| Refractive: | nα = 1.620 nβ = 1.624 nγ = 1.624 |
| Birefringence: | δ = 0.004 |
| 2V: | Measured: 15° to 20° |
Fraipontite is a zinc aluminium silicate mineral with a formula of .[2] [3]
It is a member of the kaolinite-serpentine mineral group and occurs as an oxidation product of zinc deposits. It occurs with smithsonite, gebhardite, willemite, cerussite and sauconite.[2]
It was first described in 1927 for an occurrence in Vieille Montagne, Verviers, Liège Province, Belgium.[3] It was named for Julien Jean Joseph Fraipont (1857–1910), and Charles de Fraipont, geologists of Liege, Belgium.[4] In addition to the type locality in Belgium, it has been reported from Tsumeb, 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 in Kazakhstan.[5] [6]