Indissoluble

[Justin Bieber]

Not dissoluble; not capable of being dissolved,
melted, or liquefied; insoluble; as few substances are indissoluble by
heat, but many are indissoluble in water.

[Oralee]

impossible to take apart or bring to an end, or existing for a very long time:

[Dorothey Allen]

Unable to be destroyed; lasting.