S. R. Faruqi:

Some people write ḳhākah as ḳhākā . It's possible that Mir too might have written it like this; thus I've given the preference ot ḳhākā Otherwise I myself spell it only with a h . The wordplay of ḳhāk and ḳhākā is very clear. The excellence of rom rom tan is beyond praise. It's a pity that later people have abandoned this kind of mixed [Indic and Persian] constructions and phrases.

A very small thing, too, is called a ḳhākah ; and an image made to evoke laughter, a cartoon, is called a ḳhākā . And ḳhākah-e fīrozah is the name of that precious stone that would emerge safe and unscathed from the mine, and would be fit for a ring, etc. Thus its meanings of 'small thing' and 'gemstone' have a fine affinity with 'gold mine'. And the body that glitters like gold because of the yellowness of grief-- since it's obviously less valuable than a gold mine, to call the ḳhāk-e jasad (body) a 'cartoon' (that is, ḳhākah as a term of artistic work) of a gold mine is also not inappropriate. To bestow on the yellowness produced by grief, the image of 'gold', is a very minor example of Mir's creative powers.

He has used this image in one other place as well [{401,8}]:

basān-e zar hai mirā jism-e zār sārā zard
aṡar tamām hai dil ke gudāz karne ko

[like gold, my whole wretched body is yellow
the effect is complete, of melting down the heart]

Zafar Iqbal too has versified the image of the body's and gold's both being yellow. It's probable that he might have taken this from Mir himself, because I've never seen it in the work of any other poet:

tā ṣubḥ damaktī rahī sonā sī mirī lāsh
kis zahr kī zardī thī żafar nesh-e nafas meñ

[until dawn my body kept glittering like gold,
the yellowness of what poison, Zafar, was in the sting of the breath?]

FWP:

SETS == WORDPLAY
MOTIFS
NAMES
TERMS

If every single hair on the body has been colored by the 'yellowness' or pallor of grief, then the body might be covered by a tracery of tiny points of yellowness or 'gold' color, thus making it resemble a sort of map or sketch that would outline the shape of a 'gold mine'. Moreover, zardī itself comes from zar , which adds an extra piquancy to the claim. Of course, such a body would be a pretty weird gold mine, but that's already been allowed for, since the verse itself seems a bit skeptical-- the second line with its kis is interrogatory, after all.

A gold mine is something valuable and desirable-- does that mean that the lover's suffering too somehow converts his wretched body into something much richer, or even transcendent (since gold endures almost forever)? Does it mean that some sort of virtue or richness can be excavated from his body through the painful 'digging' of grief? Or is his body a mere 'caricature' (see the definition of ḳhākā above) of a gold mine-- is it a mere 'grief mine'?

The real heart of the verse is wordplay: in addition to zar and zardī , it offers-- prominently placed so that they bracket the second line-- the enjoyable resonance of ḳhāk and ḳhākā .