The invention relates to Eu.sup.2+-activated phosphors, to a process of its preparation, the use of these phosphors in electronic and electro optical devices, such as light emitting diodes (LEDs) and solar cells and especially to illumination units comprising said magnesium alumosilicate-based phosphors.

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.

A phosphor is represented by the general formula
aM.sup.IX.Math.M.sup.II.sub.1-xM.sup.IM.sup.VO.sub.4:(Re).sub.x
where M.sup.I is at least one atomic element selected from the group consisting of K, Li, Na, Rb, Cs, Fr, Cu, and Ag, with K being essential; M.sup.II is at least one atomic element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Mn, Zn, Cd, and Sn; M.sup.V is at least one atomic element selected from the group consisting of P, V, Nb, Ta, As, Sb, and Bi; X is at least one halogen element, with F being essential; Re is at least one atomic element selected from the group consisting of rare earth elements, with Eu being essential; and a is in the range 0.6a1.4.

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.

A phosphor is represented by the general formula

aM.sup.IX.M.sup.II.sub.1-xM.sup.IM.sup.VO.sub.4:(Re).sub.x

where M.sup.I is at least one atomic element selected from the group consisting of K, Li, Na, Rb, Cs, Fr, Cu, and Ag, with K being essential; M.sup.II is at least one atomic element selected from the group consisting of Mg, Ca, Sr, Ba, Ra, Mn, Zn, Cd, and Sn; M.sup.V is at least one atomic element selected from the group consisting of P, V, Nb, Ta, As, Sb, and Bi; X is at least one halogen element, with F being essential; Re is at least one atomic element selected from the group consisting of rare earth elements, with Eu being essential; and a is in the range 0.6a1.4.