Ardennite-(As)
(Mn2+,Ca)4(Al,Mg,Mn3+)6(AsO4)(SiO4)2(Si3O10)(OH,O)6 [CNMNC approved formula]
Named in 1872 for the locality - Salmchâteau, in the Ardennes, Belgium. Renamed to ardennite-(As) with the discovery of ardennite-(V).
| IMA status : | Renamed IMA Approved; 2007 () |
| CLASSIFICATION | |
| Dana (8th edition) : |
58.03.01.01 |
| (58) Sorosilicate Insular, Mixed, Single, and Larger Tetrahedral Groups | |
| (58.03) with insular single and triple groups (n=1,3) | |
| (58.03.01) Ardennite group | |
| Nickel-Strunz (10th edition) : |
09.BJ.40 |
| (09) Silicates | |
| (09.B) Sorosilicates (dimer) structures | |
| (09.BJ) Sorosilicates with Si3O10, Si4O11, etc. anions; cations in octahedral [6] and greater coordination | |
| Crystal system: | Orthorhombic System |
| Point group (H-M): | mmm (or 2/m 2/m 2/m) — dipyramidal |
| Unit cell: | a = 8.7126 Å, b = 18.5124 Å, c = 5.8108 Å |
| Crystal Habit: | Individual crystals are rare. Crystals prismatic, acicular; crystalline aggregates and small rosettes of tapered acicular crystal |
| Color: | Yellow to yellowish brown, black |
| Diaphaneity: | Nearly opaque, translucent in thin splinters |
| Luster: | Subadamantine |
| Hardness (Mohs): | 6 - 7 |
| Measured Density: | 3.69 - 3.75 g/cm3 |
| Cleavage: | 2; {010} perfect, {110} distinct |
| Tenacity: | Brittle |
| Fracture: | Subconchoidal to uneven |
| Streak: | Pale brownish yellow |
| Geologic Setting: | In pegmatites and quartz veins in schist (Salmchateau, Belgium); in highly oxidized Mn, Al-rich metasediments (Andros Island, Greece). |
| Mineral Association: | Quartz, albite, pyrolusite, piemontite, spessartine, braunite, hematite |
| Comments: | Valid Pre-IMA 1872; Renamed to ardennite-(As) in 2007 with the discovery of ardennite-(V). |
Slender prismatic, yellow crystals to 4mm embedded in quartz matrix.Origin: Arrow Junction, Central Otago, New Zealand
Sample size: 2 x 1 x 1 cm
Photo: Tom Loomis
(zoom-in of above)