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<section end="s1"/>
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<section begin="s2"/>'''BROOKITE,''' one of the three modifications in which titanium
+
<section begin="s2"/>'''BROOKITE,''' one of the three modifications in which titanium
dioxide (TiO<sub>2</sub>) occurs in nature; the other minerals with the same chemical composition, but with different physical and crystallographic characters, being [[1911 Encyclopædia Britannica/Rutile|rutile]] (''q.v.'') and [[1911 Encyclopædia Britannica/Anatase|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.
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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.'u.).
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The two latter are tetragonal in crystallization, whilst brookite is
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orthorhombic. The name was given by A. Lévy in 182 5 in honour
−
of the English mineralogist H. ]. Brooke (1 7 7 1-18 57). Two types
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of brookite crystals may be distinguished. The commoner
−
type of crystals are thin and tabular, and often terminated by
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numerous small and brilliant faces (fig. 1); the faces of the
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orthopinacoid (a) and of the prisms (m, l) are vertically striated.
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These crystals are of a rich reddish-brown colour and are often
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translucent. Crystals of the second type have the appearance
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of six-sided bip ramids (fig. 2) owing to the equal development
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of the prism m (im) and the pyramid e {122}; tl1ese crystals are
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black and opaque, and constitute the variety known as arkansite.
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The lustre of brookite is metallic-adamantine. There is no
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distinct cleavage (rutile and anatase have cleavages); hardness
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5%-6; sp. gr. 4-0. The optical characters are interesting: the
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FIG. 1. Fig. 2.
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optic axes for red and for blue light lie in planes at right angles
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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.
−
to
each other, whilst for yellow-green light the crystals are
+
[[Image:brookite_1.png|right|172px|thumb|F<small>IG.</small>
1.]]
−
uniaxial
.
The acute bisectrix of the optic axes is perpendicular
+
[[Image:brookite_2
.
png|right|172px|thumb|F<small>IG.</small>
2.]]
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to the orthopinacoid (a) for all colours, so that this phenomenon
+
−
of the
crossing
of the
optic
axial
planes
may
be
readily
observed
+
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.
−
in the thin tabular crystals of the first-mentioned type.
+
−
Brookite
occurs
only
as
crystals
,
never
in
compact
masses
,
+
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.
−
and
is
usually
associated
with either anatase or rutile
.
The
+
{{right|([[Author:Leonard
James
Spencer|L.
J.
S
.
]])}}
−
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, l1ave
−
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)
<section end="s2"/>
<section end="s2"/>
−
<section begin="s3"/>'''BROOKLIME''', known botanically as Veronica Beccabunga
+
<section begin="s3"/>'''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.
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(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.
<section end="s3"/>
<section end="s3"/>
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<section begin="s4"/>'''BROOKLINE''', a township of Norfolk county, Massachusetts,
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<section begin="s4"/>'''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 <section end="s4"/>
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U.S.A., about 3 m. S.W. of Boston, lying immediately S. of the
−
Back Bay district. Pop. (1890) 12,103; (1900) IQ,935, of whom
−
6536 were foreign-born; (IQIO, 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<section end="s4"/>