[quote=sinner] I thought the chalice needed to be made of noble material that was not easily breakable.
You are correct. here’s what the GIRM says:
"327 Among the requisites for the celebration of Mass, the sacred vessels hold a place of honor, especially the chalice and plate, in which the bread and wine are offered, consecrated and consumed.
328 Sacred vessels are to be made from noble metal. If they are fabricated from metal which produces rust, or from a metal less noble than gold, then generally they shall be gold-plated on the inside.
329 In accord with the judgment of the Conference of Bishops, in acts confirmed by the Apostolic See, sacred vessels may be made even from other solid materials which, in the common estimation of the region are regarded as noble e.g., ebony or other hard woods as long as such materials are suited to sacred use. In such cases, preference is always to be given to materials that do not break easily or deteriorate. Materials intended for all vessels which hold the Eucharistic bread such as the plate, ciborium, theca, monstrance or others of this kind should be likewise suitable to sacred use. In the Dioceses of the United States of America, sacred vessels may also be made from other solid materials that, according to the common estimation in each region, are precious, for example, ebony or other hard woods, provided that such materials do not break easily or deteriorate. This applies to all vessels which hold the hosts such as the paten, the ciborium, the pyx, the monstrance, and other things of this kind.
330 As to chalices and other vessels that serve as receptacles for the blood of the Lord, they are to have bowls of nonabsorbent material. The base may be of any other solid and worthy material."
Since glass is not precious in the common estimation, and is easily breakable, it would seem to be unacceptable.
Hope that helps.