Rocks


 * Blocks movement and projectiles unless the player has flight or spectral tears respectively.
 * Can be destroyed with explosions and certain items like the, , , or.
 * Can fill in a 1-block wide gap when pushed in the right direction by an explosion, or with one of the abilities that allows destruction by walking onto the rock.
 * Note: With these items, it is important to walk in the direction of the gap.
 * Small chance to reveal a Crawl Space when destroyed.
 * Destroying 100 rocks will unlock the Lucky Rock trinket.

Tinted Rocks


Sometimes referred to as "Marked Rocks", they are always marked with an "x", and in some levels slightly tinted/discolored. These rocks are much less noticeable in, and  due to them being the same color as the surrounding rocks, but can still be distinguished by the "x" on the bottom right. Only one tinted rock can spawn per room.
 * Destroying 10 Tinted Rocks will unlock.
 * Destroying 100 Tinted Rocks will unlock.

Found in: Every Stage

Tinted Rocks have a chance to spawn 1-3 of the following when destroyed:
 * Soul Hearts
 * Keys
 * Bombs
 * Locked Chests (only one)
 * Normal Chests (only one)
 * Tinted Rock Spiders ( and only)
 * A combination of any of the items mentioned above
 * (after it has been unlocked)
 * Not picking up The Small Rock right after it spawned doesn't prevent other tinted rocks from spawning it again. Even though the chances are very small, you can exploit this to obtain multiple Small Rocks.

Super Special Rocks


Super Special Rocks are Tinted Rock variants whose smaller marks and lack of discoloration make them much harder to spot. Super Special Rocks take two bombs to blow up and drop the contents of two Tinted Rocks, with the exception that a single chest or appear without extra rewards.
 * The first super special rock encountered will always spawn, if it hasn't already been generated.

Only one super special rock can spawn per room, and normal tinted rock cannot appear in the same room.

Super Special Rocks are unlocked by.

Regardless of DLC version, an unlocking streak must be done with unique characters. That means each successful run must be performed with a new character for it to qualify.

Bomb Rocks


Act like rocks.

Found in: Low chance of replacing any rock.

Bomb rocks can be found anywhere a normal rock can spawn. They can only be destroyed by explosions and "stompy" items, like normal rocks. When they are destroyed, they create an explosion. Note that destroying a bomb rock next to a hole does not create a bridge as with normal rocks.

Spiked Rocks


Spiked Rocks are variants of normal rocks which hurt Isaac on contact, even if he's flying. They can fill in a 1-block wide gap like ordinary rocks, but the spikes will remain and Isaac will take damage as he steps on them.

If a Crawl space is generated with the same rock used to fill a gap, the bridge will not be spiked.

Found in:

Fool's Gold Rocks


Act like rocks. They have a small chance of replacing normal rocks, sometimes in small clusters, once unlocked.
 * Unlocked by:

Fool's Gold Rocks have a chance to spawn the following when destroyed:
 * 2-4 Pennies

Urns


Act like rocks.

Found in:

Urns have a chance to spawn the following when destroyed:
 * 1-3 Spiders
 * A few Pennies
 * Swallowed Penny
 * Swallowed Penny

Mushrooms

 * Act like rocks.

Found in:

Mushrooms have a chance to spawn the following when destroyed:
 * Pills
 * Poisonous gas, which knocks back Isaac and deals a half-heart damage. (This does not count as an explosion.)
 * Liberty Cap

Skulls


Act like rocks.

Found in:

Skulls have a chance to spawn the following when destroyed:
 * Host enemies
 * Tarot cards
 * Black Hearts
 * Runes

Marked Skulls

 * If  is unlocked, a skull marked with a small "x" will appear in  II or XL. When destroyed, it will drop.
 * If the player has, it will drop an identified Telepill.
 * May also appear in Red Rooms, even if the player is not in II or XL.

Polyps


Act like rocks.

Found in:

Polyps have a chance to spawn the following when destroyed:
 * 6 red tears in all directions and a puddle of bloody creep
 * Umbilical Cord
 * Heart pickups
 * Umbilical Cord
 * Heart pickups

Buckets


Act like rocks.

Found in:

Buckets have a chance to spawn the following when destroyed:
 * A burst of tears falling down in a small radius (Only full buckets)
 * 1-3 Striders
 * 1-3 Small Leeches
 * A few Pennies
 * Swallowed Penny
 * Swallowed Penny

Buckets in Dross additionally have a chance to spawn the following when destroyed:
 * 1-3 Drips
 * Butt Penny
 * Butt Penny