Explanatory notes
… not elsewhere specified or included. 2530.10 ‑ Vermiculite, perlite and chlorites, unexpanded 2530.20 ‑ Kieserite, … in heading 68.06 . (4) Lydite, a very hard, rough, fine‑textured and even‑grained, dark stone, not attacked by acids. Touchstones made of lydite (e.g., for testing precious metals) fall in heading 68.15 . (5) …