Vermiculite is available in various grades, with common sizes ranging from fine to coarse, suitable for different applications like gardening, packing, and insulation. For example, fine grades are used for seed sowing, while coarser grades are better for potting and cuttings. 
Here's a more detailed breakdown:
Horticultural Grades:
Fine: Suitable for seed sowing and seed starting mixes. 
Medium: Used in potting mixes, cuttings, and houseplant composts. 
Coarse: Good for water retention and aeration in growing media. 
Chunky/Ginormous: Used to increase water absorption and aeration in soil and soilless growing media. 
Other Grades:
Grade 1: For industrial spill cleanup and horticulture use. 
Grade 2: For packing hazardous liquids, meeting ICAA and IATA hazardous material requirements. 
Grade 3: Protects bottled liquids from damage and leakage. 
Grade 4: Excellent absorbent and cushioning, also meeting ICAA and IATA hazardous material requirements. 
Specific Sizes:
0-0.5mm (Grade 07): 
0-1mm (Grade 1): 
2-4mm: 
3-6mm (Grade 3): 
4-8mm (Grade 4): 
2-6mm (Coarse): 
1-3mm (Fine): 
Uses:
Packing: Absorbs liquids and provides cushioning for fragile items and hazardous materials. 
Insulation: Used as loose-fill insulation in walls and attics. 
Soil Additive: Improves water retention and aeration in soil. 
Spill Cleanup: Absorbs spills of various liquids. 
Concrete Aggregate: Used in concrete mixes