These quarto volumes, some of which are still available, record the history of the Observatory's research and activities. An attempt to spread more widely our knowledge of the composition of these remarkable organs must meet with wide approval.
Exterior form
Textures
Rose (1864) has proposed a classification of the meteorites according to their principal
- Calcium-rich stones, poor in metallic iron
- Magnesium-rich stones, poor in metallic iron
- Magnesium-rich chondritic stones with metallic iron
- Iron with silicates
- Iron meteorites
- Main constituents are py- roxenes and plagioclase
- Pyroxenes and olivine form the main constituents
- Bronzite, olivine, iron as main constituents
- Iron, forming networks, en- closing silicates: plagio-
- Iron with subordinate troi- lite, schreibersite, etc
Instead, I would like to suggest the name amphoterite; and for pure bronzites, the name diogenite.1 The new meteorite type under IV also needs a name, for which I chose grahamite;2 and finally the masses of Steinbach were considered a special type (siderophyre). 1 After Diogenes of Apollonia, who first clarified the concept of the cosmic origin and the iron-rich nature of meteorites.
Beschreibung der dargestellten Arten
The calcium-rich stones, poor in metallic iron
Another ingredient is the yellow silicate mineral that Rose observed in the form of small plates. In both cases, the anorthite contains small glass inclusions of the same shape and distribution.
The magnesium-rich stones, poor in metallic iron
Diese Mischung wurde bisher nur in einem einzigen Meteoriten gefunden, dem von Bishopville. Einschlüsse sind nur in geringen Mengen vorhanden und bestehen aus undurchsichtigen Körnchen, seltener aus schwarzen Nadeln.
Story-Maskelyne kindly made available to me the thin-section depicted in figures 17
- The magnesium-rich chondritic stones with metallic iron
- The Stony-Iron Meteorites
The grains and crystals of olivine and bronzite in the ground and chondrules are rich in glass inclusions (fig. 72). Mesosiderites.—The combination of iron with olivine and bronzite occurs in the simplest form in the Lodran meteorite, which I described some time ago (Tschermak, 1870b).
Schlussbemerkung
In some places in the meteorite, colorless transparent crystals and crystal aggregates of plagioclase with wide double lamellae appear. Some of these are free of inclusions; some contain crystalline inclusions such as those in the plagioclase of Vaca Muerta; some look dusty due to numerous very small round glass inclusions. Pallasites. In the masses of Krasnoyarsk, Brahin, Bitburg and Imilac, meteoritic iron forms a ground mass or coarse network, which encloses.
In parts of Brahin, fragments of olivine crystals are also present in the iron groundmass. Microscopically, pallasitic olivine presents nothing extraordinary, except for the tubes observed by Rose in the olivine of Krasnoyarsk; I also got it in olivine from Brahin.
Summary
Crystals in the tuffaceous chondrites are the most fractured; those in the crystalline chondrites and the stony irons, the least fractured. Also fragments of crystals are widespread in the stony irons, such as Brahin, Imilac and Vaca Muerta. Iron and pyrrhotite appear as last formed minerals in the groundmass and also impregnate the groundmass.
Iron and pyrrhotite also appear in the black veins and passage-like masses as drops and balls surrounded by black glass. In the silicate wall rocks bordering these black gangue-like masses, plagioclase and olivine have been transformed into isotropic grains (vitrified).
Erklarung der Tafel I
Brklarung der Tafel H
Brklarung der Tafel
The anorthite is similar in all respects to that of the Juvinas and Stannern eucrites, and as in the eucrites there are two kinds of augite. Other augite, such as the one at the top of the image, is brown and contains many dust-like black grains, often arranged in lines. Many bronzite crystals in the Luotolax and Massing howardites are euhedral, as shown in this figure.
The surface on the left is the 6-pinacoid (010); upper left is the brachydome (021), which commonly develops in hyperlithiasis. Many of the augite fragments in Luotolax are brown or yellow and look like terrestrial volcanic augite.
Erklarung der Tafel V
The visible long cracks correspond to the prismatic cleavage planes; several other prominent cracks run perpendicular or oblique to the prismatic cleavage. Small, rounded, brown glass inclusions are visible at the bottom of the crystal, which is surrounded by a granular mass of bronzite. In the latter, fracture occurred along the prismatic cleavage planes when the section was ground, but some of the visible fracture was probably originally present.
This photograph is a good illustration of the character of uniformly granular olivine in many stony meteorites. Small translucent particles are visible between the olivine grains, as well as colorless transparent grains like the one above right.
Erklarung der Tafel VIE
Erklarung der Tafel
Erklarung der Tafel IX
Erklarung der Tafel X
A thin olivine shell, optically continuous with the olivine interior, covers most of the chondrule surface. In the lower right, where no shell is visible, the chondrule appears incomplete, as if a piece had broken off. Black fissures in the chondrule are late fissures filled with brown material.
Each of the systems exhibits a different uniform extinction, and each alone resembles the system within the chondrule in Figure 38. A thin olivine shell is visible along much of the surface of the chondrule; this disappears with the adjacent plate system.
Erklarung der Tafel XI
On the right is a pear-shaped pyrrhotite inclusion, which was slightly damaged during grinding of the cross-section. Some leaflets radiate from the center of the chondrule, but most have different directions. The outer parts of the chondrule are gray, semi-transparent and show a very fine lattice texture in places.
Cloudy inclusions of pyrrhotite are particularly visible in the upper part of the chondrule; elsewhere they are few, sometimes forming very small star clusters. All visible white areas appear to be part of the same crystal as they die out at the same time.
Erklarung der Tafel XV
Erklarung der Tafel XVI
Um den Charakter der überwiegend glasigen Chondren in einem einzigen Bild zu veranschaulichen, wurde dieses Beispiel aus dem Chondrit von Mezo-Madaras ausgewählt, der sich in der hellbraunen Grundmasse* befindet. Eine Olivinkugel aus Porphyr, bei der die Kristalle teils dicht beieinander liegen, teils durch eine halbglasige Zwischenmasse getrennt sind, zeigt an vielen Stellen teils einzelne feine doppelbrechende Nadeln, teils netzartige Kristallisationen rechtwinklig angeordneter Nadeln und schließlich wie im vorliegenden Fall haufenweise solcher Nadeln, so dass es sich an diesen Stellen nicht um durchsichtiges Glas, sondern um eine trübe Zwischenmasse handelt, die die Olivinkristalle miteinander verbindet. In der Ausgabe von 1885 wird diese Figur abwechselnd Renazzo und Lance1 zugeschrieben.] Dargestellt ist ein Abschnitt einer porphyritischen Olivin-Chondrile, in der einige der Olivinkristalle eng zusammengepresst sind, andere durch eine halbglasartige Grundmasse getrennt.
In the latter situation, as seen in the picture, systems of fine birefringent individual needles, perpendicular crystalline networks and aggregates of needles are present. The almost colorless inclusion occurs in the upper left part of the olivine grain, which is embedded in a black groundmass.
Erklarung der Tafel XIX
Erklarung der Tafel XX
Brklarung- der Tafel XXI
Most of the chondrite, here composed of olivine and less abundant bronzite, plagioclase, and pyrrhotite grains, is intersected by two systems of fissures filled with a dull black material. Only locally is there a sharp boundary between the black mass and the surrounding body of the meteorite; in most places there is a gradual transition between the two. In the center of the black mass and parallel to its length are filaments of iron.
In addition to these, fine iron-filled transverse cracks are distinguished and are particularly clear in the lower part of the image, where they intersect an elongated iron spot. Inclusions are usually clustered in the centers of crystals; some are truncated prisms; others are triangular, almost rectangular, five-sided, or rounded in outline.
Erklarung der Tafel XXIII
Wie in Abbildung 91 ist das Olivinkorn von einer dichten Masse scheinbar gemischten Olivins umgeben. Dieses Bild stellt einen Durchschnitt des Olivins in der Masse des Lärchenholzes dar, das besonders reich an Einschlüssen ist. Eine Stelle in der Grundmasse des Hainholz-Mesosiderits, die eisenfrei ist und wenig der Oxidationsprodukte enthält, die in dieser bereits etwas verwitterten Masse häufig vorkommen.
Some of the larger inclusions appear to be parallel rod- or finger-shaped cavities, many of which are partially filled with glass. Smaller inclusions are rounded or prism-like brown glass particles and fine flecks of the same, which permeate the entire crystal.
Erklarung der Tafel XXV
Appendix
Explanation of Terms
In addition, the stage of a petrographic microscope can be rotated around the axis of the optical train, and a Bertrand lens can be placed between the upper Nicol prism and the eyepiece. In general, the polarization directions of the two components are not perpendicular to the polarization plane of the upper Nicol; hence, subcomponents of this refracted light are transmitted through the upper Nicol and reach the observer. However, when an anisotropic crystal is oriented so that the major axes of the indicatrix are parallel to the planes of polarization of the Nicol prisms, all light components are absorbed by the upper Nicol, and the crystal appears dark to the observer.
The principal axes of the indicatrix are parallel to the crystallographic axes (and thus some crystal faces and cleavage planes) in the orthorhombic, hexagonal, and tetragonal systems. The petrographic microscope becomes a conoscope by inserting the upper Nicol prism and Bertrand lens and by using a powerful objective and a strongly converging condenser system.
237 transparent minerals and are used as diagnostic
A xenoliih is a piece of rock that has been engulfed and trapped in a cooling lava or magma; it differs in composition from the surrounding igneous rock and has not been melted and assimilated by it. Whenever entities (phenocrysts, coarse fragments, chondrules, etc.) are embedded in raisin bread fashion in a strikingly different matrix (usually fine-grained), the latter is a groundmass. Chondrules in which essentially all crystalline matter is part of a single crystal (however branching or skeletal) are called monosomatic.
Veins are narrow cracks in a rock that are filled with a solid substance; they form irregular surfaces, not filaments as the word implies. By impregnation, Tschermak means the penetration of a rock zone by a mobile substance that imparts darkness or opacity to the originally transparent minerals.
In obsidians, spherulites are often the product of devitrification; these are millimeter-sized spheroids composed of very fine fibrous minerals radiating from their centers. Gangue is used to designate material that fills wider cracks and includes rock fragments; refers to the movement of material in cracks in the form of liquid.
