Glass and glass ceramic compositions having a combination of lithium silicate and petalite crystalline phases along with methods of making the glass and glass ceramic compositions are described. The compositions are compatible with conventional rolling and float processes, are transparent or translucent, and have high mechanical strength and fracture resistance. Further, the compositions are able to be chemically tempered to even higher strength glass ceramics that are useful as large substrates in multiple applications.

Crystallizable glasses, glass-ceramics, IXable glass-ceramics, and IX glass-ceramics are disclosed. The glass-ceramics exhibit -spodumene ss as the predominant crystalline phase. These glasses and glass-ceramics, in mole %, include: 60-75 SiO.sub.2; 10-18 Al.sub.2O.sub.3; 5-14 Li.sub.2O; and 4.5 B.sub.2O.sub.3. The glass-ceramics also have a Vickers initiation crack threshold of at least about 25 kgf.

Glass and glass ceramic compositions having a combination of lithium disilicate and -spodumene crystalline phases along with methods of making the glass and glass ceramic compositions are described. The compositions are compatible with conventional rolling and float processes and have high mechanical strength and fracture resistance. Further, the compositions are able to be chemically tempered to even higher strength glass ceramics that are useful as large substrates in multiple applications.

Glass-ceramics exhibiting a Vickers indentation crack initiation threshold of at least 15 kgf are disclosed. These glass-ceramics may be ion exchangeable or ion exchanged. The glass-ceramics include a crystalline and amorphous phases generated by subjecting a thin precursor glass article to ceramming cycle having an average cooling rate in the range from about 10 C./minute to about 25 C./minute. In one or more embodiments, the crystalline phase may comprise at least 20 wt % of the glass-ceramics. The glass-ceramics may include -spodumene ss as the predominant crystalline phase and may exhibit an opacity about 85% over the wavelength range of 400-700 nm for an about 0.8 mm thickness and colors an observer angle of 10 and a CIE illuminant F02 determined with specular reflectance included of a* between 3 and +3, b* between 6 and +6, and L* between 88 and 97.

Lithium disilicate-apatite glass ceramics comprising transition metal oxide are described which are characterized by a high chemical stability, and the translucence of which can be adjusted as desired, and which can therefore be used in particular as restoration material in dentistry.

What is achieved is an optical wavelength multiplexer/demultiplexer not necessarily requiring the function of adjusting the optical path. A value (L.sub.maxL.sub.min)/L obtained by dividing a difference between a maximum value L.sub.max and a minimum value L.sub.min of L in a range of 40 C. to 80 C. by L is 810.sup.6 or less where L represents a length of a crystallized glass (1) at 30 C. and L represents a difference between a length (L.sub.t) of the crystallized glass (1) at each of the temperatures and the length (L) thereof at 30 C.

Methods, compositions, and articles provide for LAS-type glass-ceramics having specific thermo-mechanical, optical and coloration characteristics to yield generally brown-grey products. The glass-ceramic materials may include as colorants iron oxide, vanadium oxide, chromium oxide, cobalt oxide, nickel oxide and/or cerium oxide.

In a Li.sub.2OAl.sub.2O.sub.3SiO.sub.2 based crystallized glass using SnO.sub.2 as a substitute fining agent for As.sub.2O.sub.3 or Sb.sub.2O.sub.3, a crystallized glass having less yellow coloration is provided at low costs. The glass is a Li.sub.2OAl.sub.2O.sub.3SiO.sub.2 based crystallized glass comprising from 0.01 to 0.9% of SnO.sub.2 in terms of % by mass and having a content of each of As.sub.2O.sub.3 and Sb.sub.2O.sub.3 of 1,000 ppm or less as a glass composition, which has a V.sub.2O.sub.5 content of from 0.08 to 15 ppm in the glass composition.

Crystallizable glasses, glass-ceramics, IXable glass-ceramics, and IX glass-ceramics are disclosed. The glass-ceramics exhibit -spodumene ss as the predominant crystalline phase. These glasses and glass-ceramics, in mole %, include: 62-75 SiO.sub.2; 10.5-18 Al.sub.2O.sub.3; 5-14 Li.sub.2O; 2-12 B.sub.2O.sub.3; and 0.4-2 Fe.sub.2O.sub.3. Additionally, these glasses and glass-ceramics can exhibit the following criteria: $a\mathrm{ratio}\text{:}\left[\underset{\_}{{\mathrm{Li}}_{2}O+{\mathrm{Na}}_{2}O+K_{2}O+\mathrm{MgO}+\mathrm{ZnO}}\right]\left[{\mathrm{Al}}_2{O}_3\right]$ between 0.8 to 1.5.
The glass-ceramics also exhibit colors at an observer angle of 10 and a CIE illuminant F02 determined with specular reflectance of a* between 0.5 and 0.5, b* between 2.5 and +2, and L* between 90 and 93.

A process for the manufacture of a glass-ceramic article exhibiting properties of resistance to scratches, greasy marks, adhesion of dirt and light scattering. The glass-ceramic article includes a surface, the surface arithmetic roughness of which is between 2 m and 7 m and the roughness being obtained using a chemical surface treatment. The glass-ceramic article is particularly suitable for use as a cooking surface and/or as surface for the preparation of foodstuffs.