pearl spar, brown spar, compound spar, rhomb spar, muricalcite, picrite, tharandite, miemite, conite, gurhofian, and, lastly, Inyo marble.

It is considered true dolomite when in chemical proportions, otherwise magnesian limestone. Its hardness is from 3-5 to 4; specific gravity, 2–9; weight of cubic foot, about 180 pounds; luster, from vitreous to earthy; color, white, various shades of rose red, gray, brown, green, or nearly black. The composition is so varied that no single analysis would convey a correct idea; when expressed by the formula, Ca O, CO2+MgO CO2, it contains

Carbonate of lime..

Carbonate of magnesia..

54.35

45.65

100.00

In Klaproth's Chemical Mineralogy, published in English in 1801, may be found detailed analyses of two specimens, one from Sweden, and the other from the Tyrol, since which time very many analyses have been made and published. Before 1791 dolomite was confounded with the limestones, until the celebrated French chemist and mineralogist, Dolomieu, called attention to it. He first noticed it among the remains of ancient sculpture in Rome. In a paper to the Journal of Physics, he described it under the name of "A calcareous stone which effervesces but little with the acids." Saussure, a Swiss naturalist, found it in place in the Alps, and named it after the original discoverer "dolomie." The present name, 'dolomite," was given to it in 1794 by Kirwan, an Irish chemist and mineralogist.

66

Dolomite was originally a sedimentary rock; this is proved by the fossils it often contains. There are several theories as to its formation, but the chemistry of its genesis is admitted to be very imperfectly understood. One theory is that it was formed in the beds of large lagoons, which became inland seas by being cut off from the ocean by some geological change in the earth's surface. As the confined water slowly evaporated, it dropped its lime, its salt, and lastly its magnesia, forming beds of dolomite. This theory is supported by the fact that beds of clay, gypsum, and rock salt are frequently found associated with dolomite. Another theory is that it was originally a precipitate let fall from the primitive sea by supersaturation, as thinolite is now being and has been formed in the alkaline lakes of the Great Basin of California, Nevada, and Utah. Still another theory assumes that the deposit was originally limestone, formed at the bottom of an ancient ocean, and that metamorphism has taken place by the addition of carbonate of magnesia from concentrated sea water, or by the abstraction of a portion of the lime by the action of water holding carbonic acid from a mineral or rock already containing a notable quantity of carbonate of magnesia. Dolomite has been formed artificially in several instances. Once in a glass flask containing a mineral water, which held bi-carbonate of lime and magnesia in considerable quantity, crystals of dolomite formed from two to three millimeters long.

Morlot produced dolomite crystals by heating carbonate of lime with solution of sulphate of magnesia in a closed tube.

Durocher subjected fragments of porous limestone in a bed of chloride of magnesium for three hours in a gun barrel kept at a red heat. Dolomite crystals formed which were stained yellow by iron. Other successful experiments of a similar nature have been recorded.

Dolomite has been used in sculpture, in architecture, and for making lime and cement. In the United States lime made of it is held in esteem,

but in England it is considered of bad quality, and is not much used. Magnesian limestones burn more easily, slake more slowly, and do not set so quickly as other limestones. As a building stone dolomite ranks among the best, but there are many different qualities, some of which are inferior to others. It is one of the chief building stones of the north of England, where a silicious dolomite is used in paving and building which gives perfect satisfaction. A yellow dolomite was used for the front of the Museum of Practical Geology in London, and the Parliament houses are built of it; but it has been shown that this stone was a failure. The commission of geologists and scientific men appointed to select a suitable stone for these buildings decided that crystalline dolomite was the best and most durable in proportion as the composition approached a mixture in chemical equivalents.

Dolomite was much used by ancient sculptors. The Apollo Belvidere, the greatest existing work of ancient art, is of dolomite. It was so called because placed in the belvidere of the Vatican. It represents the deity at the moment of his conquest of the python. The statue was found in the ruins of ancient Antium in 1503, and placed in the Vatican by Pope Julius II. Many other statues and works of art are of dolomite.

The so called Inyo marble has been selected for the building material to be used in the construction of the Sharon Gate at Golden Gate Park, and of which I am quite sure the people of San Francisco and California will be proud. It is my opinion that no use of the generous bequest could be more appropriate, or more likely to give general satisfaction, and I am fortunate in knowing by actual observation something concerning this now much-talked-of "Inyo marble."

As early as 1862 I traveled from the south side of Mono Lake to the head of Owen's Valley, then without a house or a settler north of Camp Independence. From Adobe Meadows our party of four saw for the first time the grand summit of White Mountain, capped with what seemed to be snow, slightly yellow in tint, which we attributed to the golden light of the setting sun, or dusty particles blown upon it from the desert adjacent; but snow it certainly appeared to be. When, however, we reached the base of the mountain, I discovered that the apparently snowy summit was in reality composed of a white rock; and in the rugged cañons we picked up fragments which, when freshly broken, were as pure and white as the finest Carrara marble. Subsequent chemical examination proved it to be dolomite of the finest quality. This was the now celebrated Inyo marble, which is found in numerous localities in the Inyo Range, from White Mountain south one hundred miles or more. While we make special mention here of Inyo marble, we must not for that reason omit to state that other beautiful marbles and building stones are found in those mountains, which I have seen and examined with great interest.

The most beautiful porphyries, equal to those of Egypt, are of frequent occurrence, while granite, syenite, pegmatite, and various crystalline and metamorphic rocks are met with in the sublime cañons, or lie tilted against the flanks of the higher mountains.

TECHNICAL DESCRIPTION OF INYO MARBLE.

Color, pure white, saccharoidal, cryptocrystalline, hardness between 3 and 4, scratches calc-spar with ease, specific gravity 2,856, which being the case a cubic foot will weigh 178.5 pounds avoirdupois. While in mass the mineral is resistant to crushing force, a small fragment can be crumbled between the fingers to a crystalline powder, which under the micro

scope may be seen to be obscure crystals with concave faces; some four sided pyramidal terminations are more distinct. At a red heat continued for two hours, the mineral loses 30.3 per cent by weight; the calcined mineral when wet with water becomes very hot and falls to a powder. In cold concentrated hydrochloric acid the mineral even when pulverized effervesces but feebly, but on application of heat the action is intensified, and a perfect solution is obtained which is golden yellow when concentrated, and pale straw color when dilute. The hydrochloric acid solution. becomes darker colored on addition of nitric acid, and solution of sulphocyanide of potassium imparts a deep blood red color to it. From the first solution ammonia throws down a small precipitate; the filtrate from this precipitate is colorless. Oxalate of ammonia throws down a copious precipitate; this being filtered off, phosphate of soda gives a second and also copious white precipitate. The mineral does not absorb water to any considerable extent; a fragment weighing 39.71 grains, soaked in water for twenty-four hours, increased in weight only 79 milligrams.

Before the blowpipe on charcoal the mineral falls to a powder like aragonite. This is owing to the fact revealed by the microscope that it consists of crystals distinct in themselves held together by a feeble force. In a closed glass tube the mineral gives traces only of water. These reactions show the presence of the following substances: Carbonic acid, lime, magnesia, iron, alumina. The two latter in small quantities, and traces of water. A full qualitive and quantitive analysis will be made in the future.

Measurements of the crystals, average of ten, in decimals of an inch:

Smallest.
Largest..

Average

00082 +

0

02853 +

01472 +

Mr. Israel Luce, a marble cutter of Sacramento, has given the following information as to the quarry from which the Inyo marble is to be taken to build the Sharon gate to the park: It lies a few miles from Keeler and near the lake. The exact locality is the southwest quarter of section fourteen, township sixteen south, and range thirty-seven east. It is owned by the Inyo Marble Company, incorporated last September in the State of Nevada.

A variety of dolomite has been found cropping on the Contra Costa hills, not far from the State University. When found it was said to be pozzuolana. An analysis made by Professor Rising, of the State University, gave the following result:

The rock has not been sufficiently developed to prove its quantity.

THE FOLLOWING ARE LOCALITIES

Of the principal rocks, building stones, and building materials collected by the State Mining Bureau:

1. AGALMATOLITE (?), somewhat resembling the Chinese figure stone. This beautiful ornamental stone is found two miles west of Greenwood, El Dorado County, in a vein from six inches to a foot in thickness. 2. BASALT, plains between Oroville and Pence, Butte County.

3. BASALT. Used for street pavement. Mt. Pisgah quarries, one mile south of Petaluma, Sonoma County.

4. FINE GRAINED DIORITE OR BASALT, Folsom, Sacramento County. Strongly resembling serpentine externally.

5. BUILDING STONE, Mr. Wheat's house, Double Springs, Calaveras County.

6. DIORITE, wall rock of the Clipper Gap Iron Mine, Placer County. 7. DIORITE, near the bridge, section fifteen, township eighteen north, range thirteen east, Mount Diablo meridian, Placer County.

8. DIORITE, township thirteen north, range eight east, Mount Diablo meridian, Placer County.

9. DIORITE, iron mines near Clipper Gap, section twenty-four, township thirteen north, range eight east, Placer County.

10. DIORITE, wall of furnace building, Clipper Gap Iron Mines, Placer County.

11. DIORITE, fine grained, Mineral Hill District, Mono County. It contains considerable finely divided magnetite.

12. DIORITE, fine grained, in which magnetite is replaced by pyrites, Mineral Hill, Mono County.

13. DIORITE, croppings near Cave City, Calaveras County.

14. DOLERITE, east wall, Comanche Mine, Mono County.

15. DOLOMITE, Modoc Mine, Inyo County.

16. DOLOMITE, Guadalupe Quicksilver Mine, Santa Clara County.

17. DOLOMITE (resembling fossil coral), Morro, San Luis Obispo County.

18. DOLOMITE, Deep Spring Valley, Inyo County.

19. DOLOMITE, white, Amargosa Wash, San Bernardino County.

20. DOLOMITE, Inyo County.

21. DOLOMITE, white, Tujunga Cañon, seven miles from San Fernando, San Gabriel Mountains, Los Angeles County; valuable for building and manufacturing purposes.

22. DOLOMITE (impure), found near the State University, Berkeley, Contra Costa County; mistaken for pozzuolana.

23. FOSSILIFEROUS ROCK, near Soledad, San Diego County.

24. GARNET ROCK, Calpella, Mendocino County. A large cropping. 25. GLAUCOPHANE ROCK, wall rock of the Collier Mine, six miles northeast from Murphy's, Calaveras County.

26. GNEISS, brought to San Francisco on river schooners and used for street pavements.

27. GNEISS, said to be found in San Francisco in place.

28. COARSE GRANITE, near Sacramento.

29. GRANITE, Newcastle, Placer County.

30. GRANITE, Folsom, Sacramento County.

31. GRANITE, Rocklin, Placer County.

32. GRANITE, Yosemite Valley, Mariposa County.

33. GRANITE, Mariposa Mine, Mariposa County.

34. GRANITE, Crystal Lake, Summit Valley, Nevada County. 35. GRANITE (micaceous), near Penryn, Placer County.

36. GRAVEL, San Pablo, Contra Costa County.

37. GRAVEL, distinct from the sandstone; used in macadamizing streets, Los Angeles.

38. HORNBLENDE ROCK, Santa Barbara Mountains.

39. HORNBLENDE ROCK, Healdsburg, Sonoma County.

40. HORNBLENDE ROCK, Folsom, Sacramento County.

41. HORNBLENDE ROCK, Gold Run, Placer County. 42. LAVA, Mendocino County.

43. LAVA, Napa County.

44. LAVA, compact, near St. Helena, Napa County.

45. LAVA, basaltic, near Calistoga, Napa County.

46. LAVA, red, Butte Mountain, near Jackson, Amador County.

47. LAVA, near Santa Rosa, Sonoma County.

48. LAVA, trachytic (?), which caps isolated hills between Milton and San Andreas, Calaveras County.

49. LAVA, brecciated, found in immense cliffs, Little Shasta River, Shasta County.

50. LAVA, basaltic, showing a scale, which is due to oxidation of iron to limonite, near Doon's Mill, Butte County.

51. LAVA, white (so called), indurated volcanic ash, near Murphy's, Calaveras County.

52. LAVA, which exists in immense quantities on the borders of Mono Lake, Mono County. Owens River cuts through this formation in a deep cañon. It is easily decomposed, and supposed to yield the soda salts so abundant in that region. It crops out also at Adobe Meadows, in Mono County.

53. LAVA, white (so called), probably indurated volcanic ash, Southern Pacific Railroad, Los Angeles County.

54. LAVA, and pumice, Alviso, Santa Clara County. The Guadalupe River winds through a chain of volcanic vents. They rise but a few feet above the valley.

55. LAVA, cellular, with zeolite, Soledad Cañon, Los Angeles County. 56. LAVA, cellular, Captain Jack's Cave, Modoc Lava Beds, Modoc County.

57. LIMESTONE, calcite, Santa Cruz.

58. LIMESTONE, San Bernardino County.

59. LIMESTONE, tufaceous (thinolite?), Lassen County, section thirty, township thirty north, range fourteen west.

60. LIMESTONE (marble), Clipper Gap Lime Quarry, section thirty, township thirteen north, range nine east, Mount Diablo meridian, Placer County.

61. LIMESTONE (marble), Cave Valley, near Auburn, Placer County. 62. LIMESTONE (hydraulic ?), found at the residence of Captain J. M. McDonald, San Francisco.

63. LIMESTONE (fossiliferous), Almaden Consolidated Quicksilver Mining Company, southwest quarter section thirty-four, township twentysix south, range ten east, San Luis Obispo County; elevation fifteen hundred feet.

64. LIMESTONE, Bridgeport, Mono County.

65. LIMESTONE, Tres Pinos, San Benito County, fifteen miles east of

the town.

66. LIMESTONE, Modoc Mine, Inyo County.