Tsushima Feldspar (対馬長石)
A standard material in Glazecalc's library: its oxide analysis, unity contribution and hazards.
What it is
- Kind
- Feldspars and stones
- Formula
- SiO₂ 79.17%, Al₂O₃ 12.07%, Fe₂O₃ 0.06%, TiO₂ 0.1%, CaO 0.67%, MgO 0.2%, Na₂O 6.38%, K₂O 0.41%, LOI 0.88%
- Also called
- 対馬長石, 対州長石, Taishu feldspar, Tsushima feldspar
- Sold in
- JP
- Source
- 佐賀県陶磁器原料株式会社 (Arita): 釉薬原料の化学分析表, the supplier's typical analysis of what it sells (undated; read 2026-11-04)
A typical analysis from one supplier in Arita: check it against your own supplier's. A soda feldspar with much free quartz, about 79% SiO₂ and almost no potash, not a pure feldspar. Do not swap it for a soda or potash feldspar weight for weight.
Oxide analysis and unity formula
Glazecalc has the analysis of Tsushima Feldspar (対馬長石) as weight percent of the raw material. The unity contribution is the moles of each oxide in the amount of Tsushima Feldspar (対馬長石) that holds 1.0 mole of flux, which is how Glazecalc adds it into a recipe's unity formula.
| Oxide | Weight % | Unity contribution |
|---|---|---|
| SiO₂ | 79.17 | 10.609 |
| Al₂O₃ | 12.07 | 0.953 |
| Fe₂O₃ | 0.06 | 0.003 |
| TiO₂ | 0.1 | 0.010 |
| CaO | 0.67 | 0.096 |
| MgO | 0.2 | 0.040 |
| Na₂O | 6.38 | 0.829 |
| K₂O | 0.41 | 0.035 |
- Equivalent weight
- 805.15
- Fired weight
- 798.06
- Loss on ignition
- 0.88%
The equivalent weight is the grams of Tsushima Feldspar (対馬長石) that hold 1.0 mole of flux. The fired weight is what is left of that after firing.
Hazards and safety
Hazards: Contains crystalline silica; avoid breathing the dust.
Use it in a recipe
Add Tsushima Feldspar (対馬長石) to a recipe in the Glazecalc calculator to see what it does to a glaze's unity formula.