The block also contained storerooms which held practical resources, as well as irreplaceable intellectual material.

"Baghdad is one of the great museums of the world, with irreplaceable material," said Dr. John Malcolm Russell, a specialist in Mesopotamian archaeology at the Massachusetts College of Art in Boston.

No one seems able to say how much irreplaceable material has been stolen, much less how the problem can be fought.

The present exhibition would in fact have been incomplete without her advice, her research and her discovery of irreplaceable archival material.

Mercury was in those days an irreplaceable material for the amalgamation of silver, which was one of the key sources of wealth in Latin America, especially in Mexico.

Judge Kaplan said in court yesterday: "Mr. Spiegelman, you have deprived a generation of scholars and students of the irreplaceable raw materials by which they seek to discern the lessons of the past and help us to avoid repeating it.

Damage to irreplaceable archaeological materials is only direct, as when remains are disordered, altered, destroyed, or looted, but often the indirect result of poorly planned development of tourism amenities, such as hotels, restaurants, roads, and shops.

He was, in some ways, much harder to listen to in the further disbursement of people, whom he regarded as renewable resources, and of irreplaceable material, which the colony had to conserve.

Judge Kaplan told Mr. Spiegelman that he had "deprived a generation of scholars and students of the irreplaceable raw materials by which they seek to discern the lessons of the past."

It consumes irreplaceable materials; it wears out.