ay, _Life and Works of A. L. Barye_
(1889), published by the Barye Monument Assoc. of New York; Jules Claretie,
_Peintres et sculpteurs contemporains_ (1882); Roger Ballu, _L'Oeuvre de
Barye_ (1890); Charles Sprague Smith, _Barbizon Days_ (1903).

(H. FR.)

BARYTES, a widely distributed mineral composed of barium sulphate (BaSO_4).
Its most striking feature and the one from which it derives its name
barytes, barite (from the Greek [Greek: barus] heavy) or heavy spar, is its
weight. Its specific gravity of 4.5 is about twice as great as that of salt
and of many other colourless, transparent and glassy minerals not unlike
barytes in general appearance. The mineral is usually found in a state of
considerable chemical purity, though small amounts of strontium and calcium
sulphates may isomorphously replace the barium sulphate: ammonium sulphate
is also sometimes present, whilst clay, silica, bituminous matter, &c., may
be enclosed as impurities.

[Illustration]

Crystals of barytes are orthorhombic and isomorphous with the strontium and
lead sulphates (celestite and anglesite); they are usually very perfectly
developed and present great variety of form. The simplest are rhomb-shaped
tables (fig. 1) bounded by the two faces of the basal pinacoid (_c_) and
the four faces of the prism (_m_); the angle between the prism-faces (_mm_)
is 78deg 23', whilst that between _c_ and _m_ is 90deg. The mineral has a
very perfect cleavage parallel to the faces _c_ and _m_, and the cleavage
surfaces are perfectly smooth and bright. The crystals of prismatic habit
represented in figs. 2 and 3 are bounded by the domes _d_ and _f_ and the
basal pinacoid _c_; fig. 4 is a plan of a still more complex crystal.
Twinning is represented only by twin-lamellae, which are parallel to the
planes _m_ and _f_ and are of secondary origin, having been produced by
pressure.

Crystals of barytes may be transparent and colourless, or white and opaque,
or of a yellow, brown, bluish or greenish colour. Well developed crystals
are extremely common, but the mineral occurs also in a granular, earthy, or
stalactitic condition. It is known as cawk in the Derbyshire lead mines.
The "crested" or "cock's comb" barytes occurs as rounded aggregations of
thin lamellar crystals.

Barytes is of common occurrence in metalliferous veins, especially those
which yield ores of lead and silver; some of the largest and most perfect
crystals of colourless barytes were obtained