	US 11,987,519 B2
	Glass ceramic material of a spinel type for the production of fashion jewellery and jewellery stones
Rostislav Krátký, Pencín (CZ); Jakub Altsmíd, Frýdlant (CZ); and Romana Kaluzná, Jenisovice (CZ)
Assigned to PRECIOSA, A.S., Jablonec Nad Nisou (CZ)
Filed by PRECIOSA, A.S., Jablonec nad Nisou (CZ)
Filed on Aug. 17, 2021, as Appl. No. 17/404,752.
Application 17/404,752 is a continuation of application No. PCT/CZ2019/050033, filed on Aug. 9, 2019.
Claims priority of application No. CZ2019-91 (CZ), filed on Feb. 18, 2019.
Prior Publication US 2021/0380473 A1, Dec. 9, 2021
Int. Cl. C03C 10/00 (2006.01); A44C 17/00 (2006.01)

CPC C03C 10/0054 (2013.01) [A44C 17/008 (2013.01)]

13 Claims

1. A glass ceramic material for the production of fashion jewellery and jewellery stones with a high refractive index of at least 1.62 and a high heat resistance having a melting point of at least 1550° C., characterised in that it is formed by aluminium-boron-silicate glass with the addition of ZnO and MgO oxides, which forms by subsequent heat treatment a homogeneously dispersed nanocrystalline phase consisting of (in weight %):

20-40% SiO₂,

1.5-10% B₂O₃,

20-35% Al₂O₃,

0.1-20% MgO,

0.1-20% ZnO,

while the content of MgO+ZnO is at least 10%, and

as nucleation agents for controlled bulk crystallization:

0.1-15% ZrO₂,

0-15% TiO₂,

while the content of TiO₂+ZrO₂is at least 5%.