BROOKITE, one of the three modifications in which titanium dioxide (TiO2) occurs in nature; the other minerals with the same chemical composition, but with different physical and crystallographic characters, being rutile (q.v.) and anatase (q.v.) The two latter are tetragonal in crystallization, whilst brookite is orthorhombic. The name was given by A. Lévy in 1825 in honour of the English mineralogist H.J. Brooke (1771-1857). Two types of brookite crystals may be distinguished. The commoner type of crystals are thin and tabular, and often terminated by numerous small and brilliant faces (fig. 1); the faces of the orthopinacoid (a) and of the prisms (m, l) are vertically striated. These crystals are of a rich reddish-brown colour and are often translucent. Crystals of the second type have the appearance of six-sided bipyramids (fig. 2) owing to the equal development of the prism m {110} and the pyramid e {122}; these crystals are black and opaque, and constitute the variety known as arkansite.
The lustre of brookite is metallic-adamantine. There is no distinct cleavage (rutile and anatase have cleavages); hardness 5½-6; sp. gr. 4.0. The optical characters are interesting: the optic axes for red and for blue light lie in planes at right angles to each other, whilst for yellow-green light the crystals are uniaxial. The acute bisectrix of the optic axes is perpendicular to the orthopinacoid (a) for all colours, so that this phenomenon of the crossing of the optic axial planes may be readily observed in the thin tabular crystals of the first-mentioned type.
Brookite occurs only as crystals, never in compact masses, and is usually associated with either anatase or rutile. The crystals are found attached to the walls of cavities in decomposed igneous rocks and crystalline schists; it is also found as minute isolated crystals in many sedimentary rocks. The best-known locality is Fronolen near Tremadoc in North Wales, where crystals of the thin tabular habit occur with crystallized quartz, albite and anatase on the walls of crevices in diabase. Similar crystals of relatively large size are found attached to gneiss at several places in the Swiss and Tirolese Alps. Thicker crystals of prismatic, rather than tabular, habit and of a rich red colour combined with considerable transparency and brilliancy are found in the gold-washings of the Sanarka river in the southern Urals. The arkansite variety occurs with rutile in the elaeolite-syenite of Magnet Cove in Hot Spring county, Arkansas. Minute crystals of brookite have been detected with anatase and rutile in the iron-ore of Cleveland in Yorkshire.
Crystals of brookite, as well as of anatase and rutile, have been prepared artificially by the interaction of steam and titanium fluoride, the particular modification of titanium dioxide which results depending on the temperature at which the reaction takes place. Brookite is liable to become altered to rutile: aggregates of rutile needles with the form of brookite (arkansite) are not uncommon at Magnet Cove, Arkansas.
(L. J. S.)
BROOKLIME, known botanically as Veronica Beccabunga (natural order Scrophulariaceae), a succulent herb growing on margins of brooks and ditches in the British Isles, and a native of Europe, north Africa and north and western Asia. It has smooth spreading branches, blunt oblong leaves and small bright blue or pink flowers.
BROOKLINE, a township of Norfolk county, Massachusetts, U.S.A., about 3 m. S.W. of Boston, lying immediately S. of the Back Bay district. Pop. (1890) 12,103; (1900) 19,935, of whom 6536 were foreign-born; (1910, census) 27,792. The area of the township in 1906 was 6.75 sq. m. It is served by the Boston & Albany railway, and is connected with Boston by an electric line. Brookline is the wealthiest of the residential suburbs of Boston; and contains a number of beautiful estates and homes. Within its limits are the villages of Cottage Farm, Longwood, and Reservoir Station, or Chestnut Hill—the Chestnut Hill reservoir is just beyond the township. Brookline has an excellent public library. At Clyde Park are the grounds and club-house of the Boston Country Club. Brookline has long been regarded as a model city suburb. It is connected with
Boston Common by boulevards of the Metropolitan Park System. The first settlement was probably made about 1635, and it was called Muddy River until 1705, when it was created a township under the name of Brookline. Up to 1793 it belonged to Suffolk county, of which Boston is a part, and since that time it has belonged to Norfolk county; but Boston has in its growth almost surrounded it, and because of its great wealth there has been a long struggle for and against its merger in Boston. Frederick Law Olmsted, the famous landscape gardener, had his home in Brookline, where there are various examples of his work.