Malachite is a green opaque mineral whose color indicates a salt of
copper. It is a carbonate of copper containing water, the percentages
being in the typical mineral, cupric oxide 71.9, carbon dioxide 19.9,
and water 8.2. It is the common form which copper assumes when it or
even its ores oxidize in the air. Many of the green stains on rocks or
minerals can be correctly referred to malachite. It is only valued for
ornamental purposes however when it occurs in compact masses usually
exhibiting concentric layers. Malachite in this form takes a fine
polish. Malachite is not a hard mineral, its hardness being between 3.5
and 4. It can therefore be scratched with a knife. It is comparatively
heavy, weighing four times as much as an equal bulk of water. When
heated before the blowpipe it fuses easily, coloring the flame green. By
heating long enough on charcoal it can be made to yield a globule of
copper. It is easily attacked by common acids, causing effervescence of
carbon dioxide. This test can be used to distinguish it from the
silicate of copper, chryscolla, which has the same color.
Besides its occurrence in massive forms as noted above Malachite not
uncommonly occurs in tufts and rosettes incrusting other minerals. This
is an especially common occurrence in mines in Arizona and affords
specimens of great beauty especially when the green tufts of malachite
are seen upon brown limonite, for then the appearance of moss on wood is
closely simulated. Such material is of course too fragile to be used for
decorative purposes.
Malachite is prepared for ornamental use by sawing masses of the
character of those previously referred to into thin strips which are
then fastened as a veneer on vessels of copper, slate or other stone
previously turned to the desired shape. Putting pieces together so that
neither by their outlines nor color will it appear that they are
patchwork requires a high degree of skill and such work is done almost
exclusively in Russia. Table tops, vases and various other vessels are
manufactured in this way and form objects of great beauty. The pillars
of the Church of Isaac in St. Petersburg are of malachite prepared in
this way and there are similar pillars in the Church of St. Sophia,
Constantinople, said to have been taken from the Temple of Diana at
Ephesus.
Occasionally the desired object can be turned from a single piece of
malachite, but pieces of sufficient size for this purpose are rare.
Bauer describes one piece found in the Gumeschewsk mines which was 17½
feet long, 8 feet broad and 3½ feet high and compact throughout. This is
probably the largest single mass known.
Russia furnishes most of the malachite suitable for work of this kind
and the art of cutting and fitting the stone is possessed almost
exclusively in that country. Most of the Russian malachite has been
obtained from the mines of Nischne-Tagilsk and Bogoslowsk in the
northern Urals, or Gumeschewsk in the southern. The supply has gradually
decreased till now only the Nischne-Tagilsk mines are productive. The
malachite is said to occur there in veins in limestone.
Besides the Urals, fine malachite suitable for cutting comes from
Australia. Burra Burra in New South Wales and Peak Downs in Queensland
are localities whence good Australian malachite is obtained.
Malachite as a mineral is common in copper mines in the United States
but it is only in Arizona that it is found of a quality suitable for
cutting. A variety from Morenci, Arizona, consists of malachite and
azurite and gives a combination of green and blue that is unique and
pleasing. (See colored plate.) Less use has been made of such material
for ornamental purposes than might have been for most of it has
unfortunately been smelted as a copper ore.
Malachite is rarely used for rings or small jewels but is cut into
earrings, bracelets, inkstands and similar objects. Art objects of
malachite seem to have been in much favor with Russian emperors as gifts
to contemporaneous sovereigns, and so bestowed are to be seen in
numerous palaces in Europe. Perhaps the most famous of these gifts is
the set of center tables, mantel pieces, ewers, basins and vases
presented by the Emperor Alexander to Napoleon and still to be seen in
an apartment of the Grand Trianon at Versailles.
Malachite was well known to the ancients and like other precious stones
was worn as an amulet. It was called pseudo-emerald by Theophrastus. Its
name is from the Greek malake, the word for mallows and was given
doubtless on account of its green color.
Azurite, the blue mineral which often accompanies malachite is likewise
a hydrous carbonate of copper and occasionally occurs so that it can be
used with malachite for ornamental purposes.
Oliver Cummings Farrington.
[Illustration: LEAF BUTTERFLY (INDIA).
(Kallima paralekta).
Life-size.
FROM COL. F. M. WOODRUFF.]
THE LEAF BUTTERFLY.
(_Kallima paralekta_.)
There are many instances of protective imitation or mimicry in nature,
but none are more pronounced, more perfect or more interesting than that
shown by the leaf butterflies. Briefly defined, the phenomenon of
mimicry is that relation which obtains when “a certain species of plants
or animal possesses some special means of defense from its enemies and
some other species inhabiting the same district or a part of it, and not
itself provided with the same special means of defense, closely
resembles the first species in all external points of form and color,
though often very different in structure and unrelated in the biological
order.” Many animals, such as some tree-lizards, resemble the colors of
the environment in which they live, either for protection from enemies
or in order that they may more easily catch their prey. Some arboreal
snakes hang from the boughs of trees like the drooping ends of creeping
vines.
The coloring of the under surface of the wings of the leaf butterflies
very closely resembles the color of a dried leaf. As dried leaves vary
in color and appearance, so do the butterflies vary in the color and
markings of their wings. It is said that even in the same species, the
under surface of the wings may be of various shades of brown, yellow,
ash and red. But the imitation of the dried leaf does not alone rest on
the color, for often, here and there, may be seen small groups of dark
colored spots which strikingly resemble the patches of fungi that are so
common on leaves. The mimicry of this butterfly is purely protective and
not for the purpose of deceiving its prey.
Dr. Alfred Russel Wallace in his “Malay Archipelago” writes of this
butterfly as he found it in its native element. He says, “This species
was not uncommon in dry woods and thickets, and I often endeavored to
capture it without success, for after flying a short distance it would
enter a bush among dry or dead leaves, and however carefully I crept up
to the spot, I could never discover it till it would suddenly start out
again, and then disappear in a similar place. At length I was fortunate
enough to see the exact spot where the butterfly settled, and though I
lost sight of it for some time, I at length discovered that it was close
before my eyes, but that in its position of repose it so closely
resembled a dead leaf attached to a twig as almost certain to deceive
the eye, even when gazing full upon it. I captured several specimens on
the wing, and was able fully to understand the way in which this
wonderful resemblance is produced.
“The ends of the upper wings terminate in a fine point, just as the
leaves of many tropical shrubs and trees are pointed, while the lower
wings are somewhat more obtuse, and are lengthened out into a short
thick tail. Between these two points there runs a dark curved line,
exactly representing the midrib of a leaf, and from this radiate on each
side a few oblique marks, which well imitate the lateral veins. These
marks are more clearly seen on the outer portion of the base of the
wings and on the inner side toward the middle and apex, and they are
produced by striae and markings which are very common in allied species,
but which are here modified and strengthened so as to imitate more
exactly the venation of a leaf.
“The habit of the species is always to rest on a dead twig and among
dead or dried leaves, and in this position, with the wings closely
pressed together, their outline is exactly that of a moderately sized
leaf, slightly curved or shrivelled. The tail of the hind wing forms a
perfect stalk, and touches the stick while the insect is supported by
the middle pair of legs, which are not noticed among the twigs and
fibers that surround it. The head and antennae are drawn back between
the wings, so as to be quite concealed, and there is a little notch
hollowed out at the very base of the wings, which allows the head to be
retracted sufficiently. All these varied details combine to produce a
disguise that is so complete and marvellous as to astonish everyone who
observes it; and the habits of the insects are such as to utilize all
these peculiarities, and render them available in such a manner as to
remove all doubt of the purpose of this singular case of mimicry, which
is undoubtedly a protection to the insect. Its strong, swift flight is
sufficient to save it from its enemies when on the wing, but if it were
equally conspicuous when at rest, it could not long escape extinction
owing to the attacks of the insectivorous birds and reptiles that abound
in tropical forests.”