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A crystalline glass-ceramic article composed of a cordierite phase of cordierite crystals or aggregates of near-parallel crystallites, having a formula of either Mg.sub.2 Al.sub.4 Si.sub.5 O.sub.18 or A.sub.x B.sub.y Mg.sub.2 Al.sub.4+x+2y Si.sub.5-x-2y O.sub.18. With the first formula, the average

A crystalline glass-ceramic article composed of a cordierite phase of cordierite crystals or aggregates of near-parallel crystallites, having a formula of either Mg.sub.2 Al.sub.4 Si.sub.5 O.sub.18 or A.sub.x B.sub.y Mg.sub.2 Al.sub.4+x+2y Si.sub.5-x-2y O.sub.18. With the first formula, the average size of the cordierite crystals or aggregates is less than 70 micrometers, and the mean coefficient of thermal expansion from 22.degree. C. to 800.degree. C. (CTE) is less than 9.times.10.sup.-7 /.degree. C. With the second formula, A is either sodium or potassium, B is either strontium or barium, the sum of x and y is not less than 0.01, and when either x or y equal zero, the CTE is not more than 14.times.10.sup.-7 /.degree. C. The article is especially suitable as a filter or catalyst substrate. The article is made by providing a glass having a glass compositional formula expressed in moles of oxides of either 2MgO+2Al.sub.2 O.sub.3 +5SiO.sub.2 or (x/2)A.sub.2 O+yBO+2MgO+[(4+x+2y)/2]Al.sub.2 O.sub.3 +(5-x-2y)SiO.sub.2, with A, B, and the sum of x and y as described above. The glass is melted, quenched, and crushed to a frit of median particle diameter no greater than 150 micrometers. The frit is consolidated into a body, which is then sintered for a sufficient time and temperature to devitrify the glass into a predominately cordierite-type phase and to coarsen the size of the cordierite crystals or aggregates of near-parallel crystallites to yield microcracks in the subsequently cooled body.

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[ What is claimed is:] [1.]1. A method of making a glass ceramic article, the method comprising:a) providing a glass having a glass compositional formula expressed in terms of moles of oxides selected from the group consisting of a first glass compositional formula of 2MgO+2Al.sub.2 O.sub.3 +5SiO.su

[ What is claimed is:] [1.]1. A method of making a glass ceramic article, the method comprising:a) providing a glass having a glass compositional formula expressed in terms of moles of oxides selected from the group consisting of a first glass compositional formula of 2MgO+2Al.sub.2 O.sub.3 +5SiO.sub.2 and a second glass compositional formula of (x/2)A.sub.2 O+yBO+2MgO+Al.sub.2 O.sub.3 +(5-x-2y)SiO.sub.2, wherein, when the glass is of the second formula,A is selected from the group consisting of sodium and potassium,B is selected from the group consisting of strontium and barium;and the sum of x and y is at least about 0.01;b) melting and quenching said glass;c) crushing said glass to a frit having a median particle diameter of no greater than about 150 micrometers;d) consolidating the crushed glass frit into a body;e) sintering the body for a sufficient time and temperature to devitrify the glass into a predominately cordierite phase of cordierite crystals or aggregates of near-parallel crystallites and to coarsen the size of the cordierite crystals or aggregates of near-parallel crystallites to yield microcracks in the subsequently cooled body; andf) cooling to yield a sintered body wherein when the glass is of the first glass compositional formula, the average size of the cordierite crystals or aggregates of near-parallel cordierite crystallites is less than about 70 micrometers, and the mean coefficient of thermal expansion from 22.degree. C. to 800.degree. C. is less than about 9.times.10.sup.-7 /.degree. C., and when the glass is of the second glass compositional formula, the mean coefficient of thermal expansion from 22.degree. C. to 800.degree. C. is not more than about 14.times.10.sup.-7 /.degree. C.