Frezarite is a block added by the Falling Meteors Mod, as part of the Frezarite Meteor. It emits a low level of light.
When it is obtained from a Frezarite Meteor, it is "fresh" and it can drop Frezarite Crystals. After a while, it will become "old". When "old", and when it is broken, the block will not drop anything, except some XP; the block can only be obtained through Silk Touch. However, it does not any use except for decoration purposes.