Bill Minarik#Neptunite is one of a few calcium-free titanium silicates (incl. benitoite). Seems like an obscure fact but:
#Zircon includes titanium in its structure, as a function of temperature; this can be a #geothermometer.
To standardize a microbeam analysis (like laser ablation ICPMS), we need a mineral with a known composition, lots of titanium and silica and no calcium, which has an isotope at mass 48. Neptunite and benitoite are perfect for this.
