: It WAS unique. One reason for why is that at the end of the Third Age there weren't many Elves or Dwarves left. They had grown apart and their renowned friendships were in the past. Legolas and Gimli were renaissance friends, so-to-speak.

How friendly were Celebrimbor and Narvi for instance? We know they worked together on Durin's Door, but were they truely friends, or merely collaborators with a mutual appreciation of each other's skills? The is plenty of evidence for periods of amicable relations between Dwarf and Elf communities, but is the same true of fast friendships of a personal sort. There are plenty of instances of Elf-Man friendships (as between Beleg and Beren) which were faithful to the death, but none that I can recall between Elves and Dwarves.

: However,...

: : There seem to have been quite a number of factors in the make
: : up, psychology if you like, of Elves and Dwarves which would
: : lead to a lack of understanding and empathy between the two
: : races.

: In principle I agree, but I'm not sure the psychologies of Elves and Dwarves are so easily distinguished.

The case is not without some blurring, though it seems to me that Tolkien wanted to hint at the existence of some fundamental differences between the psychology of the two races, otherwise his fairly numerous statements on the lack of empathy between them would have no basis. I agree that the history of open conflict between Elves and Dwarves does not of itself constitute a believable cause of lasting enmity.

: : First of all the Dwarves were literally "The children of a
: : lesser god" created by Aule not Eru (though he subsequently
: : adopted them). This alone might make for some suspicion of
: : their nature by the Elves. As the Dwarves were created by what
: : was a "specialist-god" the intrinsic nature of the Dwarves
: : might be expected to show rather limited or extreme traits
: : (which they do)- another reason for the Elves to find them
: : incomprehensible.

: Maybe, but Dwarves developed music, art, literature, and valued friendship, honesty, and integrity just as the Elves and Men did. I think the differences must be explored in how they used these systems to express themselves differently from Elves and Men.

: : The limited traits which would be likely to prejudice Elves
: : would include their secretiveness about their language(s). The
: : Elves who made very free with their speech to one and all (they
: : called themselves The Speakers (Quendi)) must have been baffled
: : by the Dwarves reticence.

: Tolkien actually contradicts himself on the issue of Dwarven language. They were more open about it in the early ages when they were on friendlier terms with the Elves. But the last great Dwarven linguist among the Elves was Pengolod, who fled Middle-earth after the War of the Elves and Sauron.

: : The issue of secrecy affects the Dwarves' strange lack of
: : evident females. Secretiveness does not promote understanding
: : or trust between peoples.

: This is true.

: : Also the material aquisitiveness of the Dwarves must have led
: : to Elves distrusting them. Sharp trading practice does not
: : lead to mutual esteem.

: I don't see that the Elves were any less materially aggressive. They pursued Morgoth for two reasons: revenge for Finwe's murder and anger over his plundering of Feanor's hoard. In fact, Elf-kings loved hoarded treasure. Tolkien even makes a point of this in THE HOBBIT.

: : The Dwarves appear to have lacked an appreciation of music, or
: : it was grossly different from that of Elves or Men, this would
: : have been something which would not endear them to the Elves.

: They definitely appreciated music. How different it might be from that of Elves and Men only J.R.R. Tolkien could know.

: : The Dwarves were in general monomaniacal, building, creating
: : objects of craftsmanship and amassing worldly wealth were the
: : things which chiefly mattered to Dwarves. These drives were
: : much less important to most Elves.

: These traits are almost exactly how Tolkien described the Noldor.

: : In general Elves were aware of the natural environment and
: : their creations (buildings, jewelry etc.) were made to
: : harmonise with nature, the Dwarves in contrast seem to have
: : delighted in overcoming nature and imposing their will on it.

: I would say the "naturists" among the Elves came mostly from the Nandor, though possibly also from the Nelyarin Avari. The Noldor were hardly showing much concern for the natural environment, in that they quarried stone and gems (a very destructive practice), built cities (devastating to the natural environment), and mined for ores (also destructive to the environment), and generally built up a technological civilization. Tolkien does not associate them with the waste and pollution that we associate with modern industry and technology, but then he wrote most of his material on the Elves well before pollution became the big issue that it did in the 1970s. I don't if he would have been influenced to consider that aspect of Elven and Dwarven production, but neither race is especially wasteful, and the Dwarves express their own intense interest for the environment.

: Most of the pollution in Tolkien is associated with Orcs.

: I think the differences go deeper, and for example stem from the way Aule made them. The Dwarves were design to be very tough and unyielding, because Aule knew they would live during the days of Melkor's ascendancy in Middle-earth. Their pride was less derived from the folly of a Fall than that of the Elves.