Hydrothermal zeolite that generally occurs in silica-rich environments in late states of granitic pegmatites and Si-rich basalts. Ca modifier added by zeolite nomenclatrue committee .
IMA Status:
Valid Species (Pre-IMA) 1906
Locality:
Filone della Speranza, Monte Capanne, San Piero di Campo, island of Elba, Tuscany, Italy.. Link to MinDat.org Location Data.
Name Origin:
Named after Antonio D'Achiardi (1839-1902), Professor of Mineralogy, Universit� di Pisa, Italy, who first described the mineral discovered by his son in a granitic pegmatite.
Prismatic - Crystals Shaped like Slender Prisms (e.g. tourmaline).
Habit:
Pseudo Octohedral - Crystals show an octohedral outline.
Habit:
Twinning Common - Crystals are usually twinned.
Hardness:
4-4.5 - Between Fluorite and Apatite
Luster:
Vitreous - Silky
Streak:
white
Optical Properties of Dachiardite-Ca
Gladstone-Dale:
CI meas= -0.02 (Excellent) - where the CI = (1-KPDmeas/KC) CI calc= -0.018 (Superior) - where the CI = (1-KPDcalc/KC)
KPDcalc= 0.2264,KPDmeas= 0.2269,KC= 0.2223 Ncalc = 1.48 - 1.49
Optical Data:
Biaxial (+), a=1.488-1.494, b=1.49-1.496, g=1.494-1.499, bire=0.0050-0.0060, 2V(Calc)=72-80, 2V(Meas)=58-73. Dispersion r > v strong.
Calculated Properties of Dachiardite-Ca
Electron Density:
Bulk Density (Electron Density)=2.20 gm/cc note: Specific Gravity of Dachiardite-Ca =2.18 gm/cc.
Fermion Index:
Fermion Index = 0.01 Boson Index = 0.99
Photoelectric:
PEDachiardite-Ca = 6.04 barns/electron U=PEDachiardite-Ca x relectron= 13.26 barns/cc.
Radioactivity:
GRapi = 29.16 (Gamma Ray American Petroleum Institute Units)
Concentration of Dachiardite-Ca per GRapi unit = 3.43 (%)
Estimated Radioactivity from Dachiardite-Ca - barely detectable
Chemical Formula: 
- barely detectable