Process for producing and product of a machinable crystallized glass having needle-like crystals precipitated therein

摘要

A process for producing a machinable crystallized glass having needle- like crystals precipitated therein, which comprises melting a mixture comprising from 40 to 60 mol % of SiO.sub.2, from 6 to 16 mol % of Al.sub. 2 O.sub.3, from 6 to 16 mol % of Y.sub.2 O.sub.3 and from 15 to 30 mol % of CaO, and allowing the melt to cool to have fine needle- like crystals of Ca.sub.4 Y.sub.6 O(SiO.sub.4).sub.6 precipitated.