Black
The last sat of a block's subsidy, the sat just before the next block's first sat; the mirror image of uncommon at the end of every block.
How a sat qualifies
Each block's subsidy creates a run of new sats. The last sat of that run is black: a sat with offset subsidy - 1 in its block. In epoch 0, when the subsidy was 5,000,000,000 sats, the first black sat is sat 4,999,999,999, the last sat of block 0.
Black is not one of ordinal theory's six rarity tiers (by those, it is common); it is the end-of-block counterpart of uncommon. The sat after a black sat, s + 1, is always the first sat of the next block (bar the very last sat ever mined).
The black family has its own exclusive tiers, highest first: black epic, black rare, black. The last sat of a block that ends a halving epoch or a difficulty adjustment period is counted there, not here.
A special case at the end
From block 6,720,000 on, the subsidy is a single sat, so each block's only sat is both its first and its last: uncommon (or a higher tier) and black at once. The two families are separate, so such a sat keeps one tier from each.
Why collectors care
There is one black sat per block, fixed in advance, as with uncommons. A black sat and the uncommon right after it are neighbours in sat order, so one output can hold both. The site's sales rules know this pair: an alpha uncommon sold with the black sat before it is counted as the alpha uncommon's sale, the black sat as its secondary row. Black sats that also carry another type are collected as their own categories, such as black omegas and the milestone blacks.
How many
Will ever exist: 6,926,535. Mined so far: 971,942. Extracted, held alone in small outputs: 129,979. The 2009 ones are Black in 2009: see Black 2009.
Supply and market
| Category | Will exist | Mined | Extracted | Last sale | Floor |
|---|---|---|---|---|---|
| Black | 6,926,535 | 971,942 | 129,979 | 6,000 sats | 8,499 sats |
As of block 972,427. Prices are per sat.