## 3 Results and Interpretation
### Chemical Composition and Variations
#### 3.3.1 Classification
All the glass beads were located in LCHA areas and had a low concentration of CaO and a large concentration of Al\({}_{2}\)O\({}_{3}\), regardless of their color, and the brown glass beads from tomb No. 11 were distributed along the LCA-A area and had a large concentration of Al\({}_{2}\)O\({}_{3}\). The blue glass beads from tomb No. 8 were located in the HCLA area and had a large concentration of CaO and a low concentration of Al\({}_{2}\)O\({}_{3}\) (Figure 4a). In particular, the blue glass beads from tomb No. 8 had larger concentrations of CaO in comparison with other glass beads. However, while the concentration of CaO in the glass beads was 5 to 10 wt.%, the concentration of Al\({}_{2}\)O\({}_{3}\) in light-blue and brown glass beads from tomb No. 18 was over 10 wt.%, which is extremely high (Figure 4a). It is known that sodium in ancient glass is contained in minerals (Na\({}_{2}\)CO\({}_{3}\)) or ash from plants. The chemical composition of glass varies depending on the materials used, and generally, there are differences in the concentrations of MgO and K\({}_{2}\)O. Glass can be classified as HMK (high MgO, K\({}_{2}\)O), LMHK (low MgO, high K\({}_{2}\)O), HMLK (high MgO, low K\({}_{2}\)O), and LMK (low MgO, K\({}_{2}\)O) based on the 1.5% concentrations of MgO and K\({}_{2}\)O [5; 16; 17; 20]. The compositions of seven soda glasses aside from the blue-green glass beads from tomb No. 11, which were potash glass, are displayed in Figure 4b. The graph shows that the soda glass was distributed along the LMHK and LMK areas. The blue glass beads from stone-lined tomb No. 8 were found in the LMK area, which means that they contain carbonate minerals, instead of ash from plants (Figure 4b). However, the light-blue glass beads from tomb No. 18, which were also blue-colored glass, were different in that they had larger concentrations of K\({}_{2}\)O compared with the blue  
Figure 4: Diagram comparing the CaO and Al\({}_{2}\)O\({}_{3}\) concentrations (**a**) and the MgO and K\({}_{2}\)O concentrations (**b**) in representative glass bead samples. glass beads from stone-lined tomb No. 8. The reasons may be complex and may include the composition and amount of coloring materials (Figure 4b). The green glass beads from tomb Nos. 11 and 18 had low concentrations of MgO and large concentrations of K\({}_{2}\)O, regardless of their excavation site. Unlike the green glass beads, the brown glass beads showed differences depending on their excavation site. Although the brown glass beads from tomb Nos. 11 and 18 were distributed along the LMK area, the brown glass beads from tomb No. 12 had similar concentrations of MgO but relatively greater concentrations of K\({}_{2}\)O (Figure 4b). The coloring materials, which have the greatest effect in terms of determining the color of glass, have large amounts of metal components. Identical compositions may result in different colors because of oxidation and reduction occurring at the time of firing. Additionally, various colors may result from the addition of opaque materials such as PbO and bleaching materials. Generally, the coloring materials do not exceed 5 wt.% of the total glass composition [5, 16, 17, 20]. The blue glass beads from tomb No. 8 had larger concentrations of Fe\({}_{2}\)O\({}_{3}\) in comparison with other coloring materials. The fragments of blue-green glass beads from tomb No. 11 and the light-blue glass beads from tomb No. 18, which are all blue-colored glass just like the blue glass beads from tomb No. 8, differed, as the light-blue glass beads from tomb No. 18 had low concentrations of Fe\({}_{2}\)O\({}_{3}\), CuO, and TiO\({}_{2}\). The blue-green glass beads from tomb No. 11 contained MnO, and large concentrations of copper oxide. All the green glass beads excavated from the Suchonri site contained Cu and Fe, as Cu results in a green color in oxidization firing environments. The brown glass beads from tomb Nos. 11, 12, and 18 all contained Fe\({}_{2}\)O\({}_{3}\), CuO, and TiO\({}_{2}\) in addition to MnO.