Rarity
Periodic events in Zcash give some zats a natural claim to being special.
Rarity is a convention, not a consensus rule. It picks out the first zat of each notable period in Zcash's history, so that collectors have a shared vocabulary for what makes a zat interesting.
Tiers
| Tier | Definition |
|---|---|
| Common | Any zat that is not the first zat of its block |
| Uncommon | The first zat of each block |
| Rare | The first zat of each retarget-day boundary (every 1,152 blocks, ~1 day) |
| Epic | The first zat after each halving (every 1,680,000 blocks) |
| Legendary | The first zat of each network upgrade (Sapling, Blossom, NU5, and so on) |
| Mythic | The first zat of the genesis block |
Why these boundaries
Zcash retargets difficulty every block rather than in 2,016-block epochs, so there is no Bitcoin-style adjustment period to hang rarity on. zOrdinals substitutes a fixed 1,152-block day boundary, which at the 75-second target lines up with one day of chain time. Network upgrades take the place of Bitcoin's conjunction cycles, since they are the moments where the chain's rules actually changed.
Supply
Because Zcash blocks arrive roughly eight times faster than Bitcoin's, uncommon zats are correspondingly more plentiful, while epic and legendary zats are extremely scarce — there are only a handful of halvings and upgrades in the chain's entire history.