Occurs in volcanic and sedimentary rocks. Common in altered silicic tuff., especially in saline lacustrine deposits.
IMA Status:
Valid Species (Pre-IMA) 1898
Locality:
Durkee opal mine, Suayze Creek, near Durkee, Baker Co., Oregon, USA. Proposed new type-example: Cady Mountains, California. Link to MinDat.org Location Data.
Name Origin:
From the Greek for wool, in allusion to its white, fibrous, wool-like appearance. Na modifier added by zeolite nomenclatrue committee.
Splintery - Thin, elongated fractures produced by intersecting good cleavages or partings (e.g. hornblende).
Habit:
Acicular - Occurs as needle-like crystals.
Hardness:
3.5-4 - Copper Penny-Fluorite
Luster:
Vitreous - Silky
Magnetism:
Nonmagnetic
Streak:
white
Optical Properties of Erionite-Na
Gladstone-Dale:
CI meas= 0.028 (Excellent) - where the CI = (1-KPDmeas/KC) CI calc= 0 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2272,KPDmeas= 0.2207,KC= 0.2271 Ncalc = 1.47 - 1.48
Optical Data:
Uniaxial (+), w=1.4711, e=1.474, bire=0.0191.
Calculated Properties of Erionite-Na
Electron Density:
Bulk Density (Electron Density)=2.07 gm/cc note: Specific Gravity of Erionite-Na =2.05 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEErionite-Na = 1.71 barns/electron U=PEErionite-Na x relectron= 3.55 barns/cc.
Radioactivity:
GRapi = 40.59 (Gamma Ray American Petroleum Institute Units)
Concentration of Erionite-Na per GRapi unit = 2.46 (%)
Estimated Radioactivity from Erionite-Na - barely detectable
Chemical Formula: 
- barely detectable