Incorrect mineral names are passed from miner to buyer to whole seller to you all the time. Many times, it is no ones fault as they are simply passing along the information they received. Let’s look at Arfvedsonite, Astrophyllite and Nuummite to set the record straight.
While the flashy appearance is similar, the chemical makeup is 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 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
- Name: Named for Johan A. Arfvedson (Arfwedson) (1792-1841), Swedish chemist.
Astrophyllite, as you can see 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
- Name: From the Greek “astron” for “star” and “phyllon” for “leaf”, in allusion to its habit of starburst-like sprays and micaceous cleavage.
Nuummite (Nuumite) from Greenland is the most well known. It has a unique gem quality and flash to it. Some say TRUE Nuummite ONLY comes from Greenland. To read more on alternative “Nuummite” click here.
While it does have flashes of color, it is not acicular spraying as you see in both Arfvedsonite and Astrophyllite. It is also classified as a ROCK as opposed to a mineral.
- Chemical Formula: (Mg2)(Mg5)Si8O22(OH)2
- Crystal System: Orthorhombic
- Hardness: 5.5 – 6
- Group: An unapproved name for a metamorphic rock with iridescent orthoamphiboles (Anthophyllite-Gedrite Series)
- Name: The name Nuummite means “derived from Nuuk” in Greenlandic