The original tesserae are often irregular in shape, rather than square or quadrangular, with markedly uneven surfaces. They are high in porosity and are frequently, as one would expect, quite worn. Color can also be a good arbiter. The old glass tesserae have a impressive variation in hue, lending them great visual richness. We found this to be true even within one cube, as a hue can vary from one spot of the tessera to another, but it is especially true when one examines groups of tesserae of the "same" color. The new tesserae, by contrast, tend to highly regular in shape, with the cuts that define the sides of the cubes crisp and clean. Their surfaces are often flat and even, their porosity is lower, and they do not appear worn. In color, the newer tesserae are more homogenous, both with respect to a single tessera and to a group of tesserae. It is important to assess all of these factors simultaneously, as in some instances old tesserae are extremely well preserved, and relatively regular in appearance, while the newer tesserae can occasionally have a high porosity and vary in color.
Several examples will help make these differences apparent. The first two, Figs. 11 and 12, come from the red jeweled borders ubiquitous in mosaics of the early Byzantine period. Fig. 11 represents a section of the jeweled band beneath the scene of the Visitation. The jeweled bands consist of alternating rectilinear and oval "jewels," linked by a single line of obliquely placed gold tesserae. The spaces between the jewels are punctuated by discs of white marble or stone that appear above and below the line of gold tesserae. In Fig. 11, nearly all of the tesserae in the jeweled band to the left of the white discs are old, while nearly all to those to the right are new. The old red cubes are irregular in shape, have uneven surfaces, and display a considerable variety in terms of hue. The new red, on the other hand, are more evenly cut, have crisper edges and have less variety in hue. The distinction between the "purple" tesserae is similar, although, because this color is more subtle and the tesserae less absolutely opaque, we must look a bit more closely. Here again, most of the purple tesserae to the left of the discs are old, most of those to the right are new. The "purple," used to line the edges of the red band, and particularly in this section of the jeweled band, to outline the jewels and discs, is actually a taupe-purple. Sometimes, the more translucent among the original tesserae look like a cloudy and dark amethyst. This was a color that was apparently difficult to match. The original cubes vary enormously in shade, some appearing more brown and others more purple, and also in the degree of translucency from one part of the tessera to another. But the new tesserae are far more even in color, appearing a flat light brown more than purple, and very consistently semi-opaque. This difference is most visible in Fig. 13, a detail from the scene of the Visitation. The line of tesserae at the far right of the photograph are the original purple. The taupe colored tesserae that form the horizontal band in the column as well as the line that runs along the base of the scene are meant to duplicate that purple color.