Hardness 5 to 6; sp. gr. 4·5 to 5·0, increasing with percentage of ferric oxide. Iron black, opaque; streak black to brownish-red. Lustre sub-metallic. Slightly magnetic.
The mineral is infusible; when powdered, it dissolves slowly in boiling hydrochloric acid, the filtered yellow solution giving the characteristic blue colouration of titanium salts on addition of tinfoil. In fused potassium hydrogen sulphate it dissolves readily. The variation in composition can be judged from the following limits:
| TiO₂ | Fe₂O₃ | FeO | |
|---|---|---|---|
| 3·5 | 93·6 | 3·3 | per cent. |
| 52·8 | 1·2 | 46·5 | „ |
Ilmenite is a widely distributed mineral. In crystals it occurs chiefly at Kragerö and Arendal in Norway, at Miask in the Ilmen mountains, in Dauphiné, the St. Gothard, etc.; in the massive form at Bay St. Paul, Quebec, and other localities in America; and in sands at Menaccan in Cornwall, Iserwiese in Bohemia, Puy de Dôme, dép. Haute Loire, France, and in Brazil, Australia, and New Zealand.
The mineral was discovered at Menaccan in Cornwall by McGregor, about 1790. He described it as containing iron and a new oxide; the unknown oxide was obtained in 1795 from rutile by Klaproth, who gave the name Titanium to the new metal it contained.
Short descriptions of the following titanates are also given (see [list]):
Davidite and Knopite; these are complex titanates containing elements of the cerium and yttrium groups.
Arizonite and Pseudobrookite—ferric titanates.
Perovskite, calcium titanate, and its variety Hydrotitanite.
Pyrophanite, a manganese titanate isomorphous with ilmenite, and Senaite, a species intermediate in composition between these two.