The invention relates to faceted gemstones based on a luminescent glass composition that contains particular oxides of rare earth metals and thus enables the faceted gemstones to be identified, and to a process for identifying the gemstones.

The present invention provides crystallized glass of three-dimensional shape for easily producing chemically strengthened glass of three-dimensional shape that resists damage and has exceptional transparency. This crystallized glass of three-dimensional shape: contains crystals; has light transmittance in terms of a thickness of 0.8 mm of 80% or higher; and contains 45-74% SiO.sub.2, 1-30% Al.sub.2O.sub.3, 1-25% Li.sub.2O, 0-10% Na.sub.2O, 0-5% K.sub.2O, a total of 0-15% of SnO.sub.2 and/or ZrO.sub.2, and 0-12% P.sub.2O.sub.5, these amounts expressing the oxide-based mass percentage.

A three-dimensionally shaped crystallized glass, including: a petalite crystal; and a lithium disilicate crystal, where the three-dimensionally shaped crystallized glass has an average transmittance of a light at a wavelength in a range of 380 nm to 780 nm of at least 80% in terms of a thickness of 0.8 mm, and the three-dimensionally shaped crystallized glass comprises, in mass % on an oxide basis: from 60 to 75% of SiO.sub.2; from 5 to 15% of Al.sub.2O.sub.3; from 4 to 20% of Li.sub.2O; from 0 to 4% of Na.sub.2O; from 0 to 3% of K.sub.2O; from 3 to 15% in total of at least one of SnO.sub.2 and ZrO.sub.2; and from 0.5 to 5% of P.sub.2O.sub.5.

Embodiments of the disclosure relate to glass-ceramic or crystalline article. The article includes 25 mol %silica60 mol %, 12.5 mol %alumina45 mol %, and 12.5 mol %strontium oxide45 mol %. According to certain embodiments, an interior of the article is mostly amorphous glass, and the interior is at least partially surrounded by a shell that is mostly crystalline. The shell defines a first major surface on a first side of the interior and a second major surface opposite to the first major surface on a second side of the interior. According to certain other embodiments, the article is a crystalline article in which columnar crystals grow inwardly from opposing surfaces and meet at about a midline of the article.