‘Coal’ is a 1968 poem by the African-American poet Audre Lorde (1934-92). Lorde was a self-described ‘Black, lesbian, mother, warrior, poet.’ The ‘warrior’ is as important as the other words.
Her poem ‘Coal’ is one of her most frequently anthologised, and sees Lorde harnessing the rage she feels when, for instance, she sees white people’s attitudes to black Americans. ‘Coal’ is black, of course, but if you put it under enough pressure, it can produce diamonds.
‘Coal’: analysis
‘Coal’ is divided into three stanzas and is a lyric poem, spoken by Lorde herself, or a speaker who shares many traits with Lorde, at any rate: her blackness, her political activism, and her sexuality.
The poem begins with an opening line comprising a single word, itself a single letter: ‘I’. This assertion of what is often referred to as ‘the lyric “I”’ in poetry then gives way to a two-letter word which adds one letter to that ‘I’: ‘Is’. Lorde states that ‘I’, her identity, is based in ‘the total black’: that is, her blackness, her African heritage. Just as the depths of the earth’s core are black with darkness, so Lorde, when she speaks, asserts her identity as someone whose identity is entirely bound up with her blackness, her black skin, her race.
But wait: ‘I / Is’ is different from ‘I / Am’. In other words, that opening line, it turns out, is not the personal pronoun pointing to individual experience (whether Lorde’s or some imagined speaker’s), but to the collective experience of Black identity. To say ‘I’ – whoever the ‘I’ 
might be – is to assert one’s Blackness, to speak and therefore to assert and realise it (and ‘realise’ in both senses: recognise and make real or incarnate).
From that singular (and single) ‘I’ which opened the poem solo, we come to the ‘many kinds’ of openness: for Lorde, poetry is a way of being open, of making her voice heard, and this first stanza of the poem is about speaking and being heard. The image of coal relates to blackness (or Blackness) because of the shared colour (and we should register the racially charged double meaning of her choice of word, ‘coloured’, in the poem’s sixth line), of course, but also because coal is mined from the earth using labour, much as black history is bound up with slave labour in America.
But carbon, the stuff which makes black coal, also makes bright, precious diamonds when enough heat and pressure is applied to it: when a diamond ‘comes into’ that ‘knot of flame’, it glows and sparkles and shines. Coal, then, can be transformed into something bright and visible, much as the silence of black people can be transformed into the poetry (and activism) of people like Lorde.
The reference to ‘who pays what for speaking’ acknowledges the price of breaking their silence which black people (especially black women) pay: as soon as they speak up and assert themselves, they open themselves (another ‘kind of open’, we might say, is opening oneself up to something, such as criticism or abuse) to all sorts of words in response, many of them unpleasant and judgmental.
Building on this opening stanza, the middle stanza explores ‘words’ in more detail. Some words are ‘open’ like a diamond on glass windows (diamond can cut glass, so black people can cut through the glass barrier and make themselves seen). As the diamond scrapes along the window, it screeches and ‘sings’, further drawing attention to itself, aided by the sunlight glinting on it. (Note the elemental properties to Lorde’s poem: just as that coal comes from the inside of the earth, so the diamond is augmented by the sunlight.)
But some words are like ‘stapled wagers’: compromised because the author has allowed their work to be diluted or censored so they can make it into print, ‘wagering’ on a greater degree of success if they don’t upset the apple-cart too much. This book is like a tooth that’s been pulled out by an incompetent dentist, corrupt and rotten.
Some words, by contrast, live in the poet’s throat and multiply like adders: poisonous and dangerous, like the bite of a venomous snake. Yet other words want to get out (like ‘gypsies’ they are travellers, seeking to move, never staying still for long), and are desperate to be spoken by the poet’s tongue, like young birds hatching from an egg. Yet other words ‘bedevil’ or torment the poet.
In the poem’s final stanza, Lorde asserts that love, itself a word, is another way of being open, and she returns to the image of a bright diamond shining in a ‘knot of flame’. In the poem’s final two lines, which almost form a rhyming couplet (even a heroic couplet), with ‘inside’ and ‘light’ chiming assonantly with each other and nearly rhyming perfectly, Lorde returns to that lyric ‘I’ from the poem’s first line, asserting that she is black because she was formed in the earth’s core. She urges the reader to view her words as a jewel which shines in the reader’s open light.
How should we interpret that last line? One way to analyse Lorde’s beautiful but enigmatic image is to see it as a call for readers to meet her ‘open’ words, her openness about her Blackness (and her sexuality, perhaps, as well), with an open mind of their own: to meet her halfway. Her ‘jewel’ or diamond will only shine in the open if it meets with light.
About ‘Coal’
Although ‘Coal’ is often dated to 1976, when it was reprinted in Lorde’s collection of that name, the poem had actually first appeared in Lorde’s debut collection, First Cities, in 1968 at the height of the US Civil Rights movement. The poem is written in free verse: it has no rhyme scheme, no regular metre, and uses irregular line lengths. And yet at certain moments, Lorde reveals a sense of structure which, whilst eschewing strict formal regularity, nevertheless brings the sounds of her own words together: perhaps most notably in that final ‘rhyme’ (or pararhyme) of ‘inside’ and ‘light’.