438 PROFESSOR HEDDLE ON 
1 gramme yielded— 
Ferric Oxide, , ‘ 97-049 
Ferrous Oxide, 1:105 -1:°089, . ; 1:096 
Manganous Oxide, . é 3 : ‘2 
Lime, . P , : : i : "952 
Silica, . : : ; ‘ ; . Ar 
100 : 067 
This is the first notice of this mineral as a British species. 
Ilmenite. 
I had hoped that my observations on the occurrence, and my analyses of 
ilmenite and of iserine, would at least have gone a long way in determining the 
question of the specific tdentity, or the opposite, of these substances. All that 
I can however say is, that I have been able to satisfy myself that the first named 
mineral may occur in granite, syenite, gneiss, and in primitive limestones; while 
it never, in Scotland at least, is to be found in volcanic rocks; and that the latter 
occurs in these alone, and is therefore entitled to BREITHAUPT’s name—trap- 
pisches eisenerz. Also, that the former appears in flat lamellar plates, and 
rarely in crystals ; these are unquestionably rhombohedral; while the few minute 
forms which are with the microscope to be seen among the myriad “black 
sand” grains of the latter, if they be not octahedral or cubo-octahedral, are 
portions of much more acute rhombohedrons than are to be seen among the 
faces of the ordinary crystals of ilmenite. 
That all the “black sands,” however, which are to be found in Scotland, 
—very commonly coating the bottoms of runlets of water on the roads of a 
metamorphic district after rainn—are to be set down as iserine, I very much 
doubt. Many of these may consist of comminuted ilmenite ; many are doubt- 
less magnetite. 
Ilmenite was first recognised as a British mineral by the writer, who found 
it in 1848, in flat crystals (form of fig. 8) imbedded in white quartz blocks, 
which lay upon the beach at the head of Loch Long. A year or two after- 
wards these blocks were traced by him to a belt, which occurs at a height of 
700 feet, on the east side of Crois. Since then he has found it in so many 
localities in Scotland that he sets it down as being not only one of the most 
widely distributed, but one of the most common minerals in Scotland. It is how- 
ever, though not confined thereto, very much more abundant in one special 
variety of gneiss than in all the other rocks of the country. 
This rock is a chloritic gneiss. A great belt of this rock, in. some spots 
tending to chlorite-slate, first appears in the east of the country, in the neigh- 
