Hastingstite - Encyclopedia
Class : Silicates
Subclass : Inosilicates
Crystal system : Monoclinic
Chemistry : NaCa2Fe5(Si6Al2)O22(OH)2
Rarity : Rare
Hastingsite is a sodium, calcium and iron amphibole, formerly considered a variety of "hornblende". It is now recognized as a mineral in its own right and forms a continuous series with magnesio-hastingsite, its magnesium equivalent. It is present in nepheline syenites, orthogneisses and amphibolites, as well as in certain skarns. It owes its name to its location of discovery : Hastings County (Ontario, Canada). Hastingsite forms elongated or stocky prismatic crystals with a hexagonal section, rarely doubly-terminated, with frequently rounded edges. Hastingsite is also known in more or less fibrous to bacillary masses or aggregates, sometimes grainy. The color is usually black-brown, sometimes brown.
Main photo : Hastingstite from St Christoph Mine, Saxony, Germany © Uwe Haubenreisser
Hastingstite in the World
Twinning
Twins are single or multiple and parallel to {100}.
Fakes and treatments
No fakes recorded for this mineral species.
Hardness : 5 to 6
Density : 3.35 to 3.5
Fracture : Irregular
Streak : Grey-green
TP : Translucent
RI : 1.669 to 1.705
Birefringence : 0.015 to 0.025
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None
Solubility : Insoluble
Magnetism : NoneRadioactivity : None