I did a search on the USPS site and below is what I found. I'm not an expert so… I think if on the Customs Form we put "decorative rocks" we would be fine. What does everyone think? I'm going to decorate my rock or rocks ( paint, writing, google eyes) so I will be cleaning my rock up nicely.
http://pe.usps.gov/search/jsp/search/vv_docread.jsp?k2dockey=http%3A%2F%2Fpe.usps.com%2Ftext%2Fimm%2Fimmc7_004.htm%40PE_IMM_HTML_5&serverSpec=56.0.145.56:9920&QueryParser=Simple&querytext=(soil)&dtype=2#hit0
720 Plant and Animal Quarantine Inspection
721 What Is Subject to Inspection
All packages that contain plants, plant products, soil, plant pests, plant material used for packing, animals, and animal products and byproducts, including meats, are subject to agricultural quarantine inspection by the U.S. Department of Agriculture (see DMM 601).
http://pe.usps.gov/search/jsp/search/vv_docread.jsp?k2dockey=http%3A%2F%2Fpe.usps.com%2Ftext%2Fimm%2Fimmc1_016.htm%40PE_IMM_HTML_5&serverSpec=56.0.145.56:9920&QueryParser=Simple&querytext=(PLANT%3CAND%3Erestrictions)&dtype=2#hit0
138.2 Plants
Plants, seeds, and plant materials, including fruits and vegetables, are subject to the provisions of DMM 601; Publication 14, Prohibitions and Restrictions on Mailing Animals, Plants, and Related Products; and the quarantine regulations of the country of destination. Customers can obtain information from the U.S. Department of Agriculture (USDA) Animal and Plant Health Inspection Service (APHIS) Plant Protection and Quarantine (PPQ) Programs at:
USDA APHIS PPQ
4700 RIVER RD
RIVERDALE MD 20737–1228
http://pe.usps.gov/text/Imm/ab_001.htm#ep2196797
Country Conditions for Mailing — Afghanistan
Prohibitions (130)
Coins; banknotes; currency notes (paper money); securities payable to bearer; platinum, gold or silver, manufactured or not.
Infectious materials.
Perishable biological substances.
Radioactive materials.
Restrictions
Traveler’s checks, precious stones, jewelry, and other valuable articles are admitted only in registered First-Class Mail International shipments.