Incorrect mineral names are passed from miner to buyer to wholesaler to you all the time. Many times, it is no one’s fault as they are simply passing along the information they received. Let’s look at Arfvedsonite and Astrophyllite to set the record straight.

While the flashy appearance is similar, the chemical makeup, hardness and system are completely different. This is one of those cases of misinformation that spread from supplier to vendor to seller to customer. While both do have some acicular spraying (needle-like crystals in a fan shape) that is where the comparison ends.


Arfvedsonite

Arfvedsonite is one of those tumbles I see all over, often misidentified as Astrophyllite. Even after calling the wholesaler to provide them with accurate and updated information that they could use to correct their mistake, they never did.

Arfvedsonite is a dark black/brown in color with acicular sprays of blue and/or gold.

  • Chemical Formula: [Na][Na2][Fe4 2+Fe3+]Si8O22(OH)2
  • Crystal System: Monoclinic
  • Hardness: 5-6
  • Group: Amphibole Group

Astrophyllite

Astrophyllite (see pic below) is more chocolate brown with golden copper acicular “needles” as opposed to Arfvedsonite’s dark brown/black matrix with blue and gold needles. When putting them side by side, like this, it is an obvious difference.

  • Chemical Formula: (K,Na)3(Fe,Mn)7Ti2Si8O24(O,OH)7
  • Crystal System: Triclinic
  • Hardness: 3
  • Group: Astrophyllite Group


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