Pure and Impure Sequences: Know the Difference

A pure sequence needs no substitute

Consider these diamonds:

Every rank follows the previous rank and all three cards belong to diamonds. Nothing is standing in for another card. This is a pure sequence. Adding 6 of diamonds extends the same natural run; it does not change the classification.

Use three checks: at least three cards, consecutive ranks, and one suit with no substituted card. A neat visual row is helpful, but each condition must still hold. For example, 3-4-6 of diamonds fails because the rank 5 is missing.

An impure sequence fills a missing position

Here the printed joker represents 9 of clubs:

Read the intended run as 8-9-10 of clubs. The joker fixes a specific missing position, so this is an impure sequence. It can be a valid sequence without being pure.

The joker need not sit in the middle. With a printed joker, 9 of clubs, and 10 of clubs, you could represent 8-9-10. What matters is a legal consecutive run, not the screen position of the substitute. State the intended card explicitly when practising.

A wild-rank card can sometimes be natural

Suppose sevens are wild for the round. Under the natural-use convention documented by the references below, this group remains pure:

The 7 of hearts occupies its own printed position between 6 and 8 of hearts. Now change the group:

The 7 of diamonds must substitute for 7 of hearts, making this run impure. The fact that both ordinary cards show a seven does not erase their different suits.

Practise: pure, impure, or invalid?

Assume fours are wild and the table allows natural use of wild-rank cards. Classify each group before reading the answer.

1. 2, 3, and 4 of spades: pure. The 4 is naturally in the correct place and suit.
2. Jack of clubs, queen of clubs, and 4 of diamonds: impure. The wild 4 can represent king of clubs.
3. 5 of hearts, 6 of spades, and 7 of hearts: invalid as a sequence. The 6 is neither the correct suit nor a wild card in this example.

Notice that the third group cannot be repaired simply by calling the 6 a joker. Only cards made wild by the actual rules can substitute. Changing the selected wild rank changes the exercise, so always state that assumption first.

Check purity before checking the rest

When reviewing a full hand, mark one confirmed pure sequence first. Then identify a separate second sequence. That second run may be pure too: you are not required to include an impure run.

Two joker-assisted runs do not satisfy the requirement for a pure sequence, even if both are individually valid. Likewise, one pure run plus several sets still lacks the second sequence. These are whole-hand problems, not problems with the individual groups.

Practise both checks with the complete declaration examples. Keep your named substitutions visible while learning, and recheck them whenever you move a joker to a different group.