I put together these tables below to provide a more detailed view of disenchanting results in Burning Crusade Classic. You can also use it for Classic Era realms, just ignore the disenchanting skill requirements because those were added in TBC.
Item Rarity and Type
The type and quantity of materials produced from disenchanting can vary by item type (armor or weapon), item level, and rarity. The following general rules can be used:
| Dust | uncommon armor (75%) and uncommon weapons (20%) |
| Essences | uncommon armor (20%) and uncommon weapons (75%) |
| Shards | rare equipment (100%), epic equipment below level 50 (100%), and rarely from uncommon equipment (3-5%). |
| Crystals | high-level epic equipment (100%) and extremely rarely from rare equipment (~0.5%) |
WoW Classic
Skill |
Item's level |
Dust |
Essence |
Shard / Crystal |
| 1 | 5-10 | 1-2x  Strange Dust |
1-2x  Lesser Magic Essence |
- |
| 1 | 11-15 | 2-3x Strange Dust |
1-2x  Greater Magic Essence |
 Small Glimmering Shard |
| 25 | 16-20 | 4-6x Strange Dust |
1-2x  Lesser Astral Essence |
Small Glimmering Shard |
| 50 | 21-25 | 1-2x  Soul Dust |
1-2x  Greater Astral Essence |
 Large Glimmering Shard |
| 75 | 26-30 | 2-5x Soul Dust |
1-2x  Lesser Mystic Essence |
 Small Glowing Shard |
| 100 | 31-35 | 1-2x  Vision Dust |
1-2x  Greater Mystic Essence |
 Large Glowing Shard |
| 125 | 36-40 | 2-5x Vision Dust |
1-2x  Lesser Nether Essence |
 Small Radiant Shard |
| 150 | 41-45 | 1-2x  Dream Dust |
1-2x  Greater Nether Essence |
 Large Radiant Shard |
| 175 | 46-50 | 2-5x Dream Dust |
1-2x  Lesser Eternal Essence |
 Small Brilliant Shard |
| 200 | 51-55 | 1-2x  Illusion Dust |
1-2x  Greater Eternal Essence |
 Large Brilliant Shard Nexus Crystal |
| 225 | 55-60 *** | 2-5x Illusion Dust |
1-3x Greater Eternal Essence |
Large Brilliant ShardNexus Crystal |
*** Items in the 57-60 level ranges from the Burning Crusade expansion will disenchant into Burning Crusade materials.
Burning Crusade Classic
Skill |
Item's level |
Dust |
Essence |
Shard / Crystal |
| 225 | 57-63 | 1-3x  Arcane Dust |
1-3x  Lesser Planar Essence |
 Small Prismatic Shard |
| 275 | 64-70 | 2-5x Arcane Dust |
1-2x  Greater Planar Essence |
 Large Prismatic Shard Void Crystal |