Diamond

Diamond is an item in Plants vs. Zombies and Plants vs. Zombies 2 (prior to the 2.1 update) worth $1000, the highest value of any currency item. Because of this, it is very rare.. Once dropped, the player can either tap it to grab the diamond or let a Gold Magnet pick it up.

Plants vs. Zombies

 * Defeating zombies (rarely happens although it can be common in Survival: Endless)
 * Defeating a Zombie Yeti (four, five if first time) (using I, Zombie Hack can summon many Zombie Yetis to get lots of diamonds)
 * Growing a Marigold to full size in the Zen Garden (one)
 * Growing a normal plant to full size in the Zen Garden (two)
 * First time completing Mini-games, Survivals or Puzzles (one)
 * Finding Bacon on Level 3-4 or 5-4 (one, depends on version)
 * Finding Crazy Dave's Magic Taco on Level 4-4 (one)​
 * Every three streaks in I, Zombie Endless or every ten streaks in Vasebreaker Endless (one, not always)
 * Defeating Dr. Zomboss in Adventure Mode (three)
 * Destroying graves with the Grave Buster, although it is very rare
 * Golden Sunflower Trophy (five, awarded by completing Adventure Mode and all Mini-games, Puzzle levels, and Survival levels)

Plants vs. Zombies 2 (prior to Far Future update)

 * Opening a lunchbox
 * Defeating zombies (rarely given)
 * More frequent in Endless Zones

Plants vs. Zombies 2 (Chinese version)

 * In lucky cards
 * Getting them in daily rewards
 * Buying them with real money

Lucky Spin achievement
Lucky Spin is an achievement that is earned when the player rolls three diamonds in Slot Machine. It is arguably the hardest achievement in the game because one diamond is very rare, and three is even rarer. In console versions, however, they just have to get a diamond. It won't give them anything, but two diamonds will give the player one. On the 1.02 update of the PS Vita version, however, does not involve diamonds to get the achievement; instead, three of a kind in general will get it.

Trivia

 * Diamonds have a "gleam" when they are about to be picked up. A chiming noise also is played when they appear.
 * The "gleam" is removed in Plants vs. Zombies 2, however, the chiming noise is still present.
 * The diamond resembles the blue gem from Bejeweled, one of PopCap's other games.
 * They also make the same noise as in Insaniquarium when picked up.
 * The diamond appears in the PC icons of Beghouled and Beghouled Twist.
 * In the 2.1 update of Plants vs. Zombies 2, diamonds were replaced with Gems.