Linear A is an undeciphered syllabary used between 1800-1450 BC in ancient Crete, alongside Cretan Hieroglyphs. Linear A was the official script for the palaces and cults, and Cretan Hieroglyphs were used for seals. Cretan Hieroglyphs had been in use for some time before the development of Linear A, and it is thought that the Linear A symbols may have derived from the shapes of some of the hieroglyphs.
It is not known what language the script represents. Some symbols are shared by Linear A and Linear B (which has been deciphered), but assigning the same symbol-sound associations to both scripts produces words written in Linear A which are not related to any currently known language.

Source : ScriptSource.org

The writing system was used by the Minoans (Cretans) from 1800 to 1450 BC to write what is suspected to be the Minoan language. Examples have also been found in Turkey and Israel.

So far, more than 7,000 individual signs have been identified - but not decoded.

More info : Wikipedia