## Common ground
All options refer to unmounted or mounted piezoelectric crystals used in electronic and sensing applications.
## Options at a glance
**3824.99 – Synthetic compounds**
- **Defining trait:** Made from man-made chemical compounds (e.g., Rochelle salt, barium titanate), not natural or synthetic stones.
- **Typical examples:** Rochelle salt crystals, barium titanate wafers.
- **Best fit when:** The crystal is chemically synthesized and not derived from quartz or natural minerals.
**7103.10 – Natural stones**
- **Defining trait:** Derived from naturally occurring minerals like quartz or tourmaline,未经人工合成.
- **Typical examples:** Natural quartz crystals, natural tourmaline.
- **Best fit when:** The crystal is mined and used in its natural form without synthetic processing.
**7104.10 – Natural quartz**
- **Defining trait:** Specifically from natural quartz, not synthetic or other materials.
- **Typical examples:** Raw natural quartz crystals used in oscillators.
- **Best fit when:** The product is unprocessed natural quartz, distinct from synthetic or other stones.
**7104.29 – Synthetic non-quartz stones**
- **Defining trait:** Made from synthetic materials other than quartz (e.g., lithium niobate, potassium dihydrogen phosphate), even if simply sawn.
- **Typical examples:** Synthetic lithium tantalate, synthetic ammonium dihydrogen phosphate.
- **Best fit when:** The crystal is artificially grown and not quartz or natural stone.
**7104.99 – Synthetic non-quartz stones (same as 7104.29)**
- **Defining trait:** Identical to 7104.29 in material type; likely a duplicate or outdated code.
- **Typical examples:** Same as above.
- **Best fit when:** Same as 7104.29 — but check for official updates, as this may be redundant.
**8541.60 – Mounted crystals**
- **Defining trait:** Piezoelectric crystals with electrical leads or housing (mounted), used in circuits.
- **Typical examples:** Crystal oscillators, sensor modules with metal casing.
- **Best fit when:** The crystal is integrated into a package for direct electronic use.
## Key differences
| Option | Material Source | Form | Mounting |
|-------|------------------|------|----------|
| 3824.99 | Synthetic compounds | Any | Unmounted |
| 7103.10 | Natural stones | Natural | Unmounted |
| 7104.10 | Natural quartz | Natural | Unmounted |
| 7104.29 | Synthetic non-quartz | Synthetic | Unmounted |
| 7104.99 | Synthetic non-quartz | Synthetic | Unmounted |
| 8541.60 | Any | Any | Mounted |
## How to choose
- Is the crystal made from natural stone (e.g., quartz, tourmaline)? → 7103.10 or 7104.10
- Is it synthetic but not quartz? → 7104.29 or 7104.99
- Is it a man-made chemical compound (not stone-based)? → 3824.99
- Is it mounted in a package with leads? → 8541.60
## Overlaps & pitfalls
- 7104.29 and 7104.99 appear identical; verify official tariff updates—likely redundant.
- Natural quartz (7104.10) is a subset of natural stones (7103.10); use 7104.10 if specifically quartz.
- If the crystal is synthetic and mounted, prioritize **8541.60** over material codes.
- No priority rule given—choose based on the product’s MAIN function or defining feature