Magnesio-hastingsite is a complex member of the amphibole supergroup, typically found in high-grade metamorphic environments and alkaline igneous rocks. Collectors often identify it by its dark, opaque to translucent prismatic habit and typical occurrence alongside calcium-rich silicates in skarn deposits.
Is this magnesio-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 magnesio-hastingsite with a known reference. Magnesio-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. Magnesio-hastingsite leaves a grayish white streak.
- 3Read the lusterHold the specimen under a strong light. Magnesio-hastingsite typically shows a vitreous luster.
- 4Match the color rangeCompare against the expected color range: dark green, brownish black, black.
- 5Look at form & habitCrystal system: monoclinic. Typical habit: prismatic crystals, massive, granular.
Often confused with
Magnesio-hastingsite vs. its common look-alikes — and how to tell them apart in the field.
How to tell apart: Streak differs — Magnesio-hastingsite leaves grayish white, Hornblende leaves grayish-white.
How to tell apart: Streak differs — Magnesio-hastingsite leaves grayish white, Hastingsite leaves white to light gray.
How to tell apart: Streak differs — Magnesio-hastingsite leaves grayish white, Edenite leaves white.
Often found alongside magnesio-hastingsite
Minerals reported to co-occur with magnesio-hastingsite. Spotting these in float or country rock is a strong cue you are in the right ground.
All properties
- Chemical formula
- NaCa₂(Mg₄Fe³⁺)(Si₆Al₂)O₂₂(OH)₂
- Mohs hardness
- 5-6
- Density
- 3.3-3.5 g/cm³
- Streak
- Grayish White
- Luster
- Vitreous
- Transparency
- Translucent
- Crystal system
- Monoclinic
- Crystal habit
- Prismatic Crystals, Massive, Granular
- Cleavage
- Perfect in Two Directions At 56 and 124 Degrees
- Rarity
- Uncommon
- Uses
- Collector, Scientific Research
- Host rock
- Metamorphic Rocks Like Marbles and Skarns, Also Found in Syenites
- Typical price
- $10-50 per specimen depending on size and quality
Where rockhounds find magnesio-hastingsite
Classic worldwide localities
- Ontario, Canada
- Franklin, New Jersey, USA
- Kola Peninsula, Russia
- Sogn og Fjordane, Norway
Field-hunting tip
Look in metamorphic rocks like marbles and skarns, also found in syenites country — that is the host setting where magnesio-hastingsite typically forms. If you start seeing quartz, feldspar, biotite in float, you are in the right ground. Field specimens usually show a prismatic crystals, massive, granular habit, so train your eye for that shape before scanning the outcrop.
Common questions
How do you identify magnesio-hastingsite?+
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Find magnesio-hastingsite on the map
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