HTS tariff line · chapter 25
2521.00.00
Limestone flux; limestone and other calcareous stone, of a kind used for the manufacture of lime or cement
Analysis
HTS 2521.00.00 covers limestone flux; limestone and other calcareous stone, of a kind used for the manufacture of lime or cement under heading 2521 (limestone flux; limestone and other calcareous stone, of a kind used for the manufacture…).
The normal trade relations rate here is zero, shared by about 91% of the 78 tariff lines in chapter 25, a useful check when a neighbouring dutiable line is a candidate. Free here means free of the base duty only: origin-specific Chapter 99 duties such as Section 301 can still be owed.
It is the only US line under subheading 2521.00, so the six-digit code used by every Harmonized System country and the eight-digit US line describe the same goods; a foreign tariff or an exporter's invoice showing 2521.00 points straight here.
Census statistics map these goods to NAICS 212319 (Other Crushed and Broken Stone Mining and Quarrying), an industry of 434 US establishments employing 7,059 people. That concordance is how imports of this line are compared with US output.
Every edition we compared, from Jan 2023 to Oct 2026 (Rev. 22), shows the same general rate of Free.