Shirome is a natural sulphide of lead and antimony from Choshiu or Iyo.
Professors Ayrton and Perry (Proc. Roy. Soc., 1878) give:
For mirrors of first quality:
| Copper | 75·2 |
| Tin | 22·6 |
| Iyo Shirome | 2·2 |
| ——— | |
| 100·0 | |
| ——— |
For mirrors of second quality:
| Copper | 81·3 |
| Tin | 16·3 |
| Iyo Shirome | 2·4 |
| ——— | |
| 100·0 | |
| ——— |
For mirrors of third quality:
| Copper | 87·0 |
| Tin | 8·7 |
| Iyo Shirome | 4·3 |
| ——— | |
| 100·0 | |
| ——— |
For mirrors of fourth quality: