Hastingsite is a dark-colored member of the calcic amphibole group often found in alkaline igneous environments. Collectors look for its characteristic prismatic, black-to-brownish crystals, which are visually indistinguishable from other common amphiboles without chemical analysis. It is most frequently encountered in specimens from syenite or nepheline syenite localities.
Is this hastingsite?
5-step field checkRun through these checks against the specimen in your hand. The more boxes tick, the more confident the ID.
- 1Test the hardnessTry to scratch hastingsite with a known reference. Hastingsite sits at Mohs 5-6, softer than the next harder reference, harder than the previous one.
- 2Check the streakDrag the specimen across an unglazed porcelain plate. Streak: greenish gray.
- 3Read the lusterHold the specimen under a strong light. Luster: vitreous.
- 4Match the color rangeCompare against the expected color range: black, dark green.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: tabular.
Often confused with
Hastingsite vs. its common look-alikes, and how to tell them apart in the field.
How to tell apart: Streak differs, so Hastingsite leaves greenish gray, Hornblende leaves grayish-white.
How to tell apart: Streak differs, so Hastingsite leaves greenish gray, Pargasite leaves white.
How to tell apart: Streak differs, so Hastingsite leaves greenish gray, Ferro-edenite leaves white.
Often found alongside hastingsite
Minerals reported to co-occur with hastingsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₂Fe₄Fe³⁺(Si₆Al₂)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.35-3.5 g/cm³
- Colors
- Streak
- Greenish gray
- Luster
- Vitreous
- Transparency
- Semitransparent
- Crystal system
- Monoclinic
- Crystal habit
- Tabular
- Cleavage
- Perfect on {110}, with intersections at 56° and 124°; partings on {001}, {100}
- Rarity
- Uncommon
- Uses
- Collector
- Host rock
- In nepheline syenite and granite; in schists, gneisses, tactites, and amphibolites
Where rockhounds find hastingsite
Classic worldwide localities
- Franklin, Sussex Co., New Jersey, USA
- Cornwall, Orange Co., New York, USA
- Iron Hill, Gunnison Co., Colorado, USA
- Bancroft, in Hastings Co., Ontario, Canada
- Crescent Lake, Cassiar Mountains, Yukon Territory, Canada
- Koraput, Orissa, India
Field-hunting tip
Where it forms: In nepheline syenite and granite; in schists, gneisses, tactites, and amphibolites. If you start seeing scapolite, apatite, magnetite in float, you are in the right ground. Typical habit: tabular. Train your eye for that shape before scanning the outcrop.
Common questions
How do you identify hastingsite?+
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What rocks look like hastingsite?+
What minerals are found with hastingsite?+
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Find hastingsite on the map
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