There were two main techniques in Greco-Roman mosaic: opus vermiculatum used tiny tesserae, typically cubes of 4 millimeters or less, and was produced in workshops in relatively small panels which were transported to the site glued to some temporary support. The tiny tesserae allowed very fine detail, and an approach to the illusionism of painting. Often small panels called emblemata were inserted into walls or as the highlights of larger floor-mosaics in coarser work. The normal technique was opus tessellatum, using larger tesserae, which was laid on site. There was a distinct native Italian style using black on a white background, which was no doubt cheaper than fully coloured work.
Why were black and white pieces used in most italian mosaics?
cheaper than fully coloured work

Many had considered Giovanni Battista Montini, the Archbishop of Milan, a possible candidate, but, although he was the archbishop of one of the most ancient and prominent sees in Italy, he had not yet been made a cardinal. Though his absence from the 1958 conclave did not make him ineligible under Canon Law any Catholic male who is capable of receiving priestly ordination and episcopal consecration may be elected the College of Cardinals usually chose the new pontiff from among the Cardinals who head archdioceses or departments of the Roman Curia that attend the papal conclave. At the time, as opposed to contemporary practice, the participating Cardinals did not have to be below age 80 to vote, there were few Eastern-rite Cardinals, and no Cardinals who were just priests at the time of their elevation.
Who was the Archbishop of Milan?
Giovanni Battista Montini

From the 9th to 11th century, Armenian architecture underwent a revival under the patronage of the Bagratid Dynasty with a great deal of building done in the area of Lake Van, this included both traditional styles and new innovations. Ornately carved Armenian Khachkars were developed during this time. Many new cities and churches were built during this time, including a new capital at Lake Van and a new Cathedral on Akdamar Island to match. The Cathedral of Ani was also completed during this dynasty. It was during this time that the first major monasteries, such as Haghpat and Haritchavank were built. This period was ended by the Seljuk invasion.
What was ornately carved in the 9th-11th centuries?
Armenian Khachkars