Vermiculite Grades Explained: A Buyer’s Guide | Miningsun
Exfoliated vermiculite is sold in four standard grades defined by particle size, and selecting the wrong grade for an application produces poor results regardless of quality. Grade 1 (0.5–2 mm) and Grade 2 (2–4 mm) are the horticultural grades used in seed germination, propagation mixes, potting media, and hydroponics substrates. Grade 3 (4–8 mm) is the primary construction grade for loose-fill cavity insulation, lightweight concrete, and passive fire protection of structural steel. Grade 4 (8–12 mm) is used in high-temperature applications including steel ladle topping, refractory insulation, and foundry riser sleeves. All grades are asbestos-free certified. This guide covers properties, application requirements, and a procurement checklist for international buyers.
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