The ciborium is an altar-vessel in which the consecrated particles for the Communion of the laity are kept. It need not necessarily be made of gold or silver, since the Roman Ritual (tit. cap. i, n. 5) merely prescribes that it be made ex solida decentique materia. It may even be made of copper provided it be gilt (Cong. Sac. Rit., 31 August, 1867). If made of any material other than gold, the inside of the cup must be gilt (Cong. Episc. et Reg., 26 July, 1588). It must not be made of ivory (ibid.) or glass (Cong. Sac. Rit., 30 January, 1880). Its base should be wide. its stem should have a knob, and it may be embellished and adorned like the chalice (vide supra). There should be a slight round elevation in the centre, at the bottom, in order to facilitate the taking out of the particles when only a few remain therein. 

The cover, which should fit tightly, may be of pyramidal or a ball shape, and should be surmounted by a cross. The ciborium ought to be at least seven inches high. It is not consecrated, but only blessed by the bishop or priest having the requisite faculties according to the form of the "Benedictio tabernaculi" (Rit. Rom., tit. iii, xxiii). As long as the Blessed Sacrament is reserved in it, the ciborium must be covered with a veil of precious material of white colour (Rit. Rom., tit. iv, 1, n. 5), which may be embroidered in gold and silver and have fringes about the edges. When it does not actually contain the Blessed Sacrament, this veil must be removed. Hence, after its purification at Mass, or when filled with new particles to be consecrated, it is placed on the altar, the veil cannot be put on it. Even from the Consecration to the Communion it remains covered. Just before placing it in the tabernacle after Communion the veil is placed on it. It is advisable to have two ciboria as the newly consecrated particles must never be mixed with those which were consecrated before. In places in which Holy Communion is carried solemnly to the sick, a smaller ciborium of the same style is used for this purpose. The little pyx used for carrying Holy Communion to the sick is made of the same material as that of which the ciborium is made. It must be gilt on the inside, the lower part should have a slight elevation in the centre, and it is blessed by the form "Benedictio tabernaculi" (Rit. Rom., tit. viii, xxiii). The ciborium and pyx lose their blessing in the same manner as the chalice loses its consecration.[1]