Low temperature zeolite found in a wide variety of geologic environments: volcanic rocks, metamorphic rocks, pegmatites, tuffs, and deep-sea sediments.
IMA Status:
Approved IMA 1998 (Dana # Added)
Locality:
Albero Bassi, Vicenza, Italy. Link to MinDat.org Location Data.
Name Origin:
Named after the English mineral collector, John Henry Heuland (1778-1856), a British mineral collector and dealer. The K-dominant member of the heulandite series.
Brittle - Generally displayed by glasses and most non-metallic minerals.
Habit:
Crystalline - Coarse - Occurs as well-formed coarse sized crystals.
Habit:
Tabular - Form dimensions are thin in one direction.
Hardness:
3-3.5 - Calcite-Copper Penny
Luster:
Vitreous - Pearly
Streak:
white
Optical Properties of Heulandite-K
Gladstone-Dale:
CI meas= 0.016 (Superior) - where the CI = (1-KPDmeas/KC) CI calc= 0.046 (Good) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2178,KPDmeas= 0.2248,KC= 0.2283 Ncalc = 1.5 - 1.52
Optical Data:
Biaxial (+), a=1.476-1.506, b=1.479-1.51, g=1.479-1.517, bire=0.0030-0.0110, 2V(Calc)=0-76, 2V(Meas)=10-48. Dispersion r > v.
Calculated Properties of Heulandite-K
Electron Density:
Bulk Density (Electron Density)=2.22 gm/cc note: Specific Gravity of Heulandite-K =2.20 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEHeulandite-K = 6.23 barns/electron U=PEHeulandite-K x relectron= 13.83 barns/cc.
Radioactivity:
GRapi = 47.06 (Gamma Ray American Petroleum Institute Units)
Concentration of Heulandite-K per GRapi unit = 2.12 (%)
Estimated Radioactivity from Heulandite-K - barely detectable
Chemical Formula: 
- barely detectable