These glass fragments originate from parts of ancient blown glass vessels of the Roman Byzantine Empire between 1st-6th centuries A.D - shortly after glass was invented. 
These glittering glass fragments were picked up on ancient sites in Israel. Some fragments are transparent while others are colored. 
The spectrum of colors which appear on the glass were formed over hundreds of years. The beautiful colors are the result of the combined effects of climatic conditions and the surrounding earth in which the glass was embedded. 
Over generations, layer upon layer of earth covered the glass, giving the unique color of "patina". Although these glass fragments are solid and do not break easily, it is advisable to handle them with care. 
It is recommended that the Roman Glass not be placed under water. The patina can wear off and cause the glass to turn black.