generic definite article with uncountable/mass nouns after preposition 'of' indicating material

Question

The 'generic' subclass of the definite article treated in the pag. 112, section 1.12.3.1 of the Modern Written Arabic: A Comprehensive Grammar reads as follows

"it denotes a generic meaning مائدة من النحاس المحفور 'a table of engraved brass’, contrasting with other possible materials. Indefinite phrases also occur in a similar sense, عوارض غليظة من خشب ‘rough joists of wood’, but here the intention is not generic but rather ‘made of some kind of wood’ with no particular contrast with any other possible material."​

The second volume of V. Cantarino's Syntax of Modern Arabic Prose, the expanded sentence, remarks that it's used 'after a determinative' and examplifies it in page 274 with the sentences صليب من الذهب 'a cross of gold', سرير من خشب 'a wooden bed' or ثوب من الخرير الأبيض 'a dress of white silk'.

However, I cannot find anything similar taken into account in generalist theories, although it seems to be a clear exception.

First, I cannot make sense of the contradictory english wording, so I'd like to find an elaboration thereof using more technical linguistic terminology.

The relation between 'Definiteness vs. Uniqueness/Specificity' could be the crux of the matter.

Answer 1

If we translate the two sentences, preserving the definite/indefinite articles, we would get something like:

1. مائدة من النحاس المحفور = a table of (the) engraved brass Of course in English, you would not typically use the in this context.

2. عوارض غليظة من خشب = rough joists of (some) wood

In practice, often the definite or indefinite forms would be used interchangeably, as is the case in the two examples. If anything, I would tend to attribute the use of definite form (مائدة من النحاس المحفور) as serving to place emphasis on النحاس المحفور = the engraved brass, taking emphasis away from the object مائدة = a table.

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The text claims that the purpose is for contrast, interpreting the following as contrastive:

مائدة من النحاس المحفور = a table of brass - not any brass - of engraved brass

And this as not contrastive:

مائدة من نحاس محفور = a table of engraved brass

And similarly, interpreting this as contrastive:

عوارض غليظة من الخشب = rough joists, made of not any wood - but some specific wood

And this as not contrastive:

عوارض غليظة من خشب = rough joists made of wood

While that is a possible interpretation of such constructions (use of the definite form), I would not go as far as to claim that this is often the intention of these constructions.