Popular Science Monthly/Volume 28/January 1886/Agatized and Jasperized Wood of Arizona

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AGATIZED AND JASPERIZED WOOD OF ARIZONA.
By GEORGE F. KUNZ.

UNDOUBTEDLY one of the greatest of American wonders is the silicified forest in Arizona, known as Chalcedony Park—a park only in name, however, for the giant trees which once grew there have long since fallen and silicified into agate and jasper. It is situated eight miles south of Corriza, a station on the Atlantic and Pacific Railroad, in Apache County, Arizona, twenty-four miles south-east of Holbrook. This marvelous deposit of probably a million tons of silicified trees covers a thousand acres. The wood is generally found projecting from the volcanic ash and lava, which is covered with sandstone to the depth of from twenty to thirty feet, and lies exposed in the gulches and basins where the water has worn away the sandstone.

The silicification probably took place in the following manner: The trees were overthrown and covered with volcanic ashes and tufa, the heated silicified waters, either gushing from springs or forced up by the violent volcanic action which felled the trees, percolated through the ashes, cooled on reaching the tree-level, and thus produced conditions favorable to silicification.

The moisture in the tufa may have effected a partial alteration, as also any waters that may have filtrated through it from rains or springs either hot or cold. Under these circumstances decomposition would be assisted and much silica be set free. The waters would become charged with this, the silica being held partly in solution similar to that in liquid glass, the silicate of soda of commerce. The silicious water then slowly penetrated the wood buried in the tufa and was slowly deposited in the cells of the wood. In this manner the fibers of the wood were replaced by the silica. The process was evidently a slow one, and the trees, from all appearances, were partly decayed and water-logged when the silicification took place. The jasper and agate generally replaced the cell-walls and fibers, and the transparent quartz filled the cells and interstices, especially where the structure was broken down by decay. These cell-centers and cavities produced the conditions favorable not only for the deposition of the silica as quartz, but also for the formation of the drusy, crystalline cavities of quartz and amethyst that enhance the beauty of the material so much. It is evident, from the rich variety of colors, that the waters held oxides of iron and perhaps manganese, as well as silica, the red color being caused by hematite, the yellows and browns by limonite, and the black by oxides of manganese.

It is possible also that the ash was deposited partly in water and thus heated it. There is every indication that the deposit is of
 
PSM V28 D375 Chalcedony park looking north.jpg
"chalcedony park" looking north.
 

considerable depth. Over the entire area the trees lie scattered in all conceivable positions and in fragments of all sizes, sometimes resembling a pile of cart-wheels. A tree one hundred and fifty feet in length is often found broken up into as many sections of almost uniform length, presenting the appearance of having been sawed asunder for shingle-block by some prehistoric forester.

Again, we find a giant tree broken into countless fragments, ranging in size from a small pebble to a fair-sized bowlder. Perfect-shaped cubes, ready to be polished and used for paper-weights, are also found. These multiplied fractures are the result of alternate heat and cold acting on the water collected in the fissures of the tree.

The highest point in the park is some two hundred feet above the surrounding level, and it is here that the buried trees can be seen to the best advantage. Some of them are one hundred and fifty feet long and ten feet in diameter, and lie exposed in all conceivable positions. One section of a tree, which has been broken up, measures eight feet in diameter, ten feet in length, and weighs several tons. The tree was originally about two hundred feet long. Some pieces of the trunks of these trees, which were brought to New York, ranged from eight inches to three feet in diameter, and from twenty-five to one thousand pounds in weight. The perfect preservation of these trunks is remarkable. The rings are so distinctly visible as to convince even the most incredulous of their organic origin.

The most interesting points in the park have been suggestively named. The Agate or Natural Bridge, Agate Gulch, Amethyst Point, Fort Jasper, etc.

The most remarkable feature of the park, and a phenomenon perhaps unparalleled, is the Natural Bridge, of agatized wood, formed by a tree, spanning a canon forty-five feet in depth and fifty-five in width. In addition to the span, fully fifty feet of the tree rests on one Bide, making the tree visible for a length of over one hundred feet. Both ends of the tree are imbedded in the sandstone. It averages three and a half feet in diameter, four feet at the thickest part, and three at the smallest. Where the bark does not adhere, the characteristic colors of jasper and agate are to be seen.

Although silicified wood is found in many localities throughout the world, nowhere is it so beautifully colored as at this place. Here we have every imaginable shade of red, yellow, brown, and green. Sometimes the colors appear in distinct spots, forming a mottled appearance; then, again, all blend so imperceptibly as to make a much more pleasing and harmonious effect than the decided banding of the agate, where the lines of demarkation between the colors are so distinct as to become obtrusive. The colors above mentioned are often relieved by white, black, and gray, and by transparent spaces of brilliant quartz crystals, or—as sometimes occurs—of amethyst.

Broken sections of the hollow trunks are often lined with amethyst. quartz, and calcite, which add their brilliancy to the endless variety of color.

Beautiful as the wood is to the naked eye, a microscope is needed to reveal its true beauty. Not only does the glass enhance the colors, but it also renders visible the structure, which has been perfectly preserved even to the forms of the minute cells, and is more beautiful now than before the transformation.

Dr. P. H. Dudley, of New York, microscopically examined some sections of this wood, and finds that part of it at least belongs to the genus Araucaria. He says that the Araucaria excelsa, the Norfolk Island pine of the South Pacific Ocean, grows to a height of from one hundred and fifty to two hundred feet. In radical longitudinal section, the lenticular markings on the wood-cells near each end are in double rows and contiguous, the markings of one row alternating with those of the other, giving the appearance of the beautiful hexagonal markings of this genus. In central portions of the cells sometimes only one row of markings is seen, and some cells show only one row. Medullary rays were indistinct.

Other portions resembled our red cedar (Juniperus Virginianus) when grown in the extreme South. The cell-structure of some indicates a growth in a mild and uniform climate, the annular rings being marked only by one, two, three, or more, slightly smaller hexagonal or rounded cells, not tabular, as is usually the case. The cell-walls were nearly uniform in thickness. All the specimens examined showed that the wood originally was undergoing decay before being filled with the various media which afterward solidified. On some of the specimens traces of fungi (mycelium), causing decay, were discovered. The beauty of the wood is largely due to the destructive influence of fungi.

Agate-cutting has been carried on as an industry for over three hundred years, in the Oberstein district, in Germany, but little attention has been paid heretofore to the cutting of large masses, because few agates are found over a foot in diameter, and the banding is not such as to offer much inducement. But in the future this material will doubtless be in great demand for interior house-decoration, where it can be advantageously used as inlays in wood or stone; for paneling and wainscoting walls; for tiling; and, if desired, for entire floors. Whole table-tops could be made of the largest size from a single section of one of these giant trees, and the design would be Nature's own incomparable handiwork. For mosaic-work it would also find a ready use, since the infinite diversity of color would afford an ample field for the imagination of the skillful artisans employed at this industry.

The rich, warm, blending colors, and the remarkable polish that this material is susceptible of, are the main features that will always give it a high place among minerals of its class. In fact, it is a question
 
PSM V28 D378 Natural bridge of agatized wood.jpg

NATURAL BRIDGE OF AGATIZED WOOD.

 

whether any of the ornamental stones, such as jade, jasper, agate, or even the marbles, have the two desired qualities to such a degree.

As before stated, the deposit has been estimated at a million tons, but probably not more than a thousand tons would be suitable for the purposes of art, while for finer work only a small part of this would be available. One instance should be noted to show the high estimation in which this wood is held by foreigners. A Russian dealer recently paid five hundred dollars for a piece twenty-eight inches in diameter and thirty inches in length, to be cut into table-tops. A large lot was recently sent abroad for cutting, and we shall soon have a new decorative stone which will possess what very few now in use do—the proper hardness.

A piece of this material was selected by Mr. Joseph Pulitzer, to form the base for the beautiful silver center-piece, which is being made by Messrs Tiffany & C, to be given as a testimonial to the eminent sculptor, F. A. Bartholdi. This base is a low truncated pyramid, eleven inches square at the base, nine inches at the top, and seven and half inches high, and is made of a single section of a tree. It was chosen on account of its superior hardness and the warmth and pleasing combination of its colors. Besides, as the designer remarked, it is eminently fitting that the testimonial should rest "on a solid American base."

This is the largest piece of such hard material that has ever been cut into a definite shape in the United States.

One of the recent freaks of fashion has been the revival of the old Scotch jewelry. The leading objection to this is the stiffness of the designs. These have in many instances, however, been Americanized and improved upon; the tame, uninteresting bloodstones and agates giving place to our own richer and brighter stones and silicified woods.