U.S. Customs Classification of Building Stone

Marble Vs. Limestone Vs. Serpentine
   Worked monumental/building stone and articles of monumental/building stone (other than articles of precious or semiprecious stone) are classifiable in Chapter 68 of the HTS. While genuine marble is classified in subheading 6802.91, HTS, limestone and serpentine (although often referred to as marble in the trade) may not be classified as marble in subheading 6802.91.
   Marble is a metamorphic rock formed when a change takes place in another rock (limestone). When the smaller calcium carbonate particles in limestone recrystallize into larger calcium carbonate particles, marble is formed.
   Although limestone and marble are chemically identical (both based on calcium carbonate), they are physically very different because of the difference in particle size. Geologists regard marble and limestone as two distinct stones because of the physical difference between them.
   Although a commonly accepted commercial definition equates polished limestone or limestone capable of taking a polish with marble, U.S. Customs follows geological definitions in the classification of stone. Since marble and limestone are regarded as distinct geologically, limestone cannot be classified as marble. While genuine marble is classifiable in subheading 6802.91, HTS, limestone is classified as other calcareous stone in subheading 6802.92.
Serpentine is often referred to as “marble” or “green marble” in the trade. However, it is geologically distinct from marble. While the essential component of marble is calcium carbonate, serpentine is based on magnesium silicate.
   Since they are two different stones, serpentine cannot be classified as marble. While genuine marble is classified in subheading 6802.91, HTS, serpentine is classified as other stone in subheading 6802.99 when in the form of building stone (slabs or tiles) or as articles of semiprecious stone in subheading 7116.20 when in the form of articles. 
Notes 1(d) to Chapter 68 of the HTS and 1(a) to Chapter 71 indicate that articles of precious or semiprecious stone must be classified in Chapter 71, not Chapter 68.
   Under the HTS, articles of serpentine are regarded as articles of semiprecious stone; therefore, articles of serpentine (e.g., vases, figurines, other articles) are classified in subheading 7116.20.  However, we classify building stone (slabs and tiles) of serpentine as other stone in 6802.99. (According to the latest Headquarters rulings, unassembled fireplace surrounds of serpentine are regarded as building stone classifiable in subheading 6802.99, not articles classifiable in 7116.20. Note ruling 959301, 10-09-97.)
   Editor's note: Since original publication of this article, rulings on marble and granite, as well as court decisions, may change some of the above information. For any updated information , please contact the U.S. Customs and Border Protection office.

Granite Vs. Other Stones
  While genuine granite is classified as granite in subheading 6802.93, HTS, other stones often referred to as granite in the trade (basalt, gabbro, diorite, syenite and gneiss) are classified as other stone in subheading 6802.99.
  Among other components, the principal ingredients in genuine granite are alkali feldspars and quartz. Basalt, diabase, diorite and gabbro are often referred to commercially as “granite” or “black granite.” However, these stones are regarded as geologically distinct from granite.
  While genuine granite contains alkali feldspars and quartz, the principal ingredients (among other components) in the “black granites” are plagioclase feldspars and quartz. Since basalt, diorite, diabase and gabbro are geologically different from granite, they cannot be classified as granite in subheading 6802.93. They are classified as other stone in 6802.99.
   Both granite and syenite contain alkali feldspars. However, granite contains quartz as an important ingredient, while syenite contains little or no quartz. This difference makes granite and syenite two geologically distinct stones. Since they are geologically different, syenite may not be classified as granite in subheading 6802.93, despite the fact that it is often referred to as granite in the trade. Syenite is classified as other stone in subheading 6802.99.
  Gneiss is often referred to in the trade as granite. Since gneiss is a metamorphic rock that may be derived from the recrystallization of granite, the two stones may be chemically identical; however, they are physically different. Gneiss is a metamorphic rock characterized by layers of compositional banding, a physical form that is very different from granite.
Geologists regard gneiss as a different stone from granite because of the physical difference between these two rocks. Since they are geologically distinct, gneiss may not be classified as granite in subheading 6802.93. It is classified as other stone in subheading 6802.99.

The Form of the Stone
   Up to this point, we have discussed stone within the context of Chapter 68 of the Harmonized Tariff Schedule of the United States (HTS).  While worked stone and articles of stone are generally classifiable in Chapter 68, stone which is crude, roughly trimmed, or merely cut by sawing or otherwise into rectangular blocks or slabs is classifiable in Chapter 25. 
   While headings 2515 and 2516 cover monumental and building stone which is crude and very slightly worked, monumental/building stone worked beyond the point of simple cutting from the quarry block is classifiable in heading 6802.  Within headings 6802, 2515 and 2516, there are various subheadings that make distinctions based on the precise degree to which the stone has been worked. 
   In addition, classification within various subheadings of headings 2515 and 2516 (like classification under various subheadings of heading 6802) must be based on the geological identity of the stone.
   The precise extent to which a stone has been worked prior to importation is a crucial factor in our determination of the correct classification.