Aluminosilicate, refractive index

The diffraction pattern was almost identical with that of normal aluminosilicate analcime. The lattice constant was calculated to be a = 13.35 0.01A by indexing the x-ray reflections, assuming that the phase has cubic symmetry. The value is slightly smaller than the average one, 13.6A, for normal analcime (7). The crystals were optically isotropic and the refractive index was 1.519 0.002, higher than that of normal analcime, 1.48. These differences in the value of lattice constant and refractive index may result from the existence of beryllium occupying a... 

Figure 16 Refractive index profile of a 5 mm diameter titanium aluminosilicate GRIN glass rod. (From Ref. 68.)...

Plagioclase feldspar (Na-Ca aluminosilicate), other than albite, stains red potash feldspar (microcline or orthoclase) stains yellow, and quartz and glassy slag are unstained. Calcite takes on various shades of pink and dolomite may be deep red. The particles are normally examined in immersion mounts, utilizing liquids of known index of refraction and a cover glass. 

Other additives to alter the properties of the glass are called intermediates. The addition of PbO to increase the index of refraction and to provide shielding from x-rays is an example. Aluminosilicate glasses are considerably stronger than soda-lime glasses and are used for reinforcing fibers, glass wool for insulation, as well as for optical applications. 

---