Larimar
Last updated: April 2026
The blue gem variety of pectolite, found only in the Los Chupaderos mine area of Barahona Province, Dominican Republic. The blue color derives from copper substituting for calcium in the crystal structure. Sky blue to blue-green with white patterns created by radiating fibrous crystal structure.
Larimar has a specific gravity of 2.80 and a refractive index of 1.595–1.640, with a Mohs hardness of 4.5–5.0. It is biaxial +.
Physical & Optical Properties
Measured with a polariscope, a refractometer, a hydrostatic balance, a Chelsea filter, a UV torch, a loupe, a darkfield loupe and a spectroscope — step-by-step for each.
Through the refractometer
Drawn from the refractive index above, on a 1.40–1.81 scale. How to take this reading.
Key Differentiators
- Sky blue color with distinctive white radiating or cloud-like patterns unique to pectolite
- Low hardness 4.5–5 — easily scratched with a knife blade
- Exclusively from Barahona Province, Dominican Republic — single world locality
- Silky fibrous radiating texture visible under loupe
- Lower RI (1.595–1.640) and different texture vs blue turquoise (1.610–1.650)
Common Simulants
- Blue Turquoise: Turquoise has waxy luster, no fibrous radiating texture, RI 1.610–1.650, SG 2.60–2.85. Lacks the pectolite radiating pattern.
- Blue Calcite: Calcite SG ~2.71, lower hardness (3), effervesces with acid, RI 1.486–1.658 with extreme birefringence.
- Blue Glass: Glass lacks fibrous texture, isotropic under polariscope, SG varies widely, typically cold to touch.
- Dyed Howlite: Dyed howlite shows dye in cracks under loupe, acetone removes dye, SG ~2.53, hardness only 3.5, strong LW fluorescence in undyed areas.
Treatments
- Wax or Resin Impregnation (surface stabilization)
Measurement Guides
Identifying a larimar? Loupewise walks through these tests in order — RI, SG, fluorescence, and more.
Try Loupewise Free →Studying for the GIA, FGA, or FEEG practical? Larimar is one of the 132 species in Loupewise’s drill and exam pool — practice identifying it from its measured properties under timed exam conditions.
Practice exams →