Minecraft wiki entry for Development, associated text: General
Added clouds.
New textures for cobblestone and planks.
Blocks
Added:
Sand and gravel.
They fall to the ground when placed. [1]
Coal, iron and gold ore.
Logs and leaves.
Terrain
New terrain generator.
Added trees, beaches of sand and gravel and naturally spawning ore veins.
Reference
[1]
Rotab's IRC logs, May 25th, 2009 (UTC +2)
"(00:03:06) <@notch> you can't make roofs out of sand and gravel [...] (00:03:14) <@notch> they fall down when there's air beneath them"