| Loellingite | |
|---|---|
 Sharp, lustrous loellingite (and/orarsenopyrite) crystals to 4 mm ongossan matrix. Locality:Broken Hill Ore Deposit,New South Wales, Australia. Size: 2.4 × 2.2 × 2.0 cm. | |
| General | |
| Category | Arsenide mineral |
| Formula | FeAs2 |
| IMA symbol | Lö[1] |
| Strunz classification | 2.EB.15a |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pnnm |
| Unit cell | a = 5.16, b = 5.93 c = 3.05 [Å]; Z = 2 |
| Identification | |
| Color | Steel grey to silvery white |
| Crystal habit | Prismatic to pyramidal crystals, massive |
| Twinning | On {001}, possibly trillings, polysynthetic on {101} |
| Cleavage | Rare, distinct on {010}, {101} |
| Fracture | Uneven |
| Mohs scale hardness | 5–5.5 |
| Luster | Metallic |
| Streak | Grayish black |
| Specific gravity | 7.1–7.5 |
| Optical properties | Distinctly anisotropic in reflected light |
| References | [2][3][4] |
Loellingite, also spelledlöllingite, is anironarsenide mineral with formula FeAs2. It is often found associated witharsenopyrite (FeAsS) from which it is hard to distinguish.Cobalt,nickel andsulfur substitute in the structure. Theorthorhombic lollingite group includes thenickel iron arseniderammelsbergite and the cobalt iron arsenidesafflorite.Leucopyrite is an old synonym for loellingite.
It forms opaque silvery whiteorthorhombic prismatic crystals often exhibitingcrystal twinning. It also occurs in anhedral masses and tarnishes on exposure to air. It has aMohs hardness of 5.5 to 6 and a quite highspecific gravity of 7.1 to 7.5. It becomes magnetic after heating.
Loellingite was first described in 1845 at the Lölling district inCarinthia,Austria, for which it was named.
It occurs in mesothermalore deposits associated with skutterudite, native bismuth,nickeline, nickel-skutterudite,siderite andcalcite. It has also been reported frompegmatites.[4]
