Format: 76 cases and 7 continuous variables.
Description: The columns are:
1. RI refractive index
2. Na2O sodium oxide (unit measurement: weight percent in
corresponding oxide, as are the rest of attributes)
3. MgO magnesium oxide
4. Al2O3 aluminum oxide
5. SiO2 silcon oxide
6. K2O potassium oxide
7. CaO calcium oxide