Silica Containing Patents (Class 501/53)
- And halogen or nitrogen (Class 501/56)
- And lead (Class 501/60)
- And phosphorus, niobium, or tantalum (Class 501/63)
- And yttrium or rare earth (i.e., elements with atomic numbers 39 or 57-71) (Class 501/64)
- And boron (Class 501/65)
- And aluminum or iron compound (Class 501/68)
- And divalent metal oxide (e.g., oxides of zinc, cadmium, beryllium, alkaline earth metal, magnesium, etc.) (Class 501/72)