Sample No.:	ALH 99500
Location:	Allan Hills
Field No.:	12065
Dimensions (cm):	3.0x1.5x1.5
Weight (g):	13.596
Meteorite Type:	CM2 Chondrite

   

Macroscopic Description: Kathleen McBride
60% of the exterior of this carbonaceous chondrite has fractured purplish black fusion crust. The exposed interior appears to have a greenish tint. The matrix is made up of soft, chalky black material that has a sulfurous odor. Contained within the matrix are tiny white chondrules.

Thin Section (, 4) Description: Tim McCoy and Linda Welzenbach

Plane-Polarized Light	Cross-Polarized Light

The section consists almost entirely of Fe-rich serpentine, which forms the matrix of the meteorite and has replaced the bulk of most chondrules. A few scattered anhydrous silicates remain. Olivine ranges from Fa_1-47, with many Fa_0-1. The meteorite is a CM2 chondrite. Pairing with ALH 83100 should be considered.

Macroscopic Description: Kathleen McBride
The entire exterior surface of this carbonaceous chondrite is covered with thick black fusion crust with polygonal fractures. The interior is black, earthy material with a sulfurous odor. This meteorite has an oxidation rind and rust halos.

Thin Section (, 4) Description: Tim McCoy and Linda Welzenbach

Plane-Polarized Light	Cross-Polarized Light

The section consists of large (up to 2 mm), well-defined chondrules in a matrix of finer-grained silicates, sulfides and abundant magnetite. The meteorite is extensively shocked and brecciated. Olivine is relatively homogeneous Fa_30-33. In this section, we observed a 1.5 by 2 mm CAI consisting of anorthite, fassaite and pleonaste spinel. A very unusual feature of this meteorite is the presence of FeO-rich phyllosilicates, which occur as veins and patches. The phyllosilicates also appear to cross cut the brecciated texture and are sometimes associated with magnetite. The origin of these phyllosilicates (terrestrial vs. extraterrestrial; timing relative to metamorphism and brecciation) is uncertain. The meteorite is a CK4 chondrite. However, phyllosilicates have not been previously reported in CK chondrites and large CAIs are very rare. This specimen is clearly very unusual.

Macroscopic Description: Kathleen McBride
The exterior has thick black fusion crust with polygonal fractures on its entire surface. The matrix is black, charcoal-like with an oxidation rind. The meteorite contains white and rust colored chondrules/inclusions, less then 1 mm in size.

Thin Section (, 3) Description: Tim McCoy and Linda Welzenbach
The section consists of small chondrules (rarely up to 1 mm), mineral grains and CAIs set in a black matrix; rare metal and sulfide grains are present. Olivine compositions are Fa_0-51, with many grains Fa_0-1. A single orthopyroxene is Fs₁. The matrix consists dominantly of an Fe-rich serpentine. The meteorite is a CM2 chondrite

Thin Section (, 2) Description: Tim McCoy and Linda Welzenbach

Plane-Polarized Light	Cross-Polarized Light

The section exhibits isolated pyroxene and plagioclase grains up to 0.5 mm. The section contains one part in which the groundmass is finely comminuted pyroxene and plagioclase grains, while the groundmass in the other is a fine-grained, lath-like structure suggestive of an impact melt. Pyroxene (Fs_24-52Wo_2-40) includes low-FeO orthopyroxene, moderate FeO pigeonite and low-FeO augite. Plagioclase exhibits a range of compositions (An_86-95Or_0-1). The meteorite is a howardite.

Macroscopic Description: Kathleen McBride
50% of this ordinary chondrite's exterior is covered with smooth brown/black fusion crust with oxidation halos. Thin fractures penetrate the surface. The interior matrix is light gray in color but most areas are rusty due to a high concentration of metal.

Thin Section (, 2) Description: Tim McCoy and Linda Welzenbach

Plane-Polarized Light	Reflected Light

The meteorite is an equilibrated L6 chondrite (Fa₂₃, Fs₂₀). An exceptional feature is the presence of a 4 by 2 mm shock melt vein characterized by a fine-grained quenched textured matrix, which includes mosaicized mafic silicate enclaves and rounded metal-sulfide blebs. No ringwoodite was noted.

Macroscopic Description: Cecilia Satterwhite
The exterior is mostly brown with about 10% of black fusion crust. The interior is dark brown to black with some light colored crystalline faces in one area and some areas that are highly oxidized.

Thin Section (, 2) Description: Tim McCoy and Linda Welzenbach
The section consists of one portion which is an interlocking fabric of isolated pyroxene grains and basaltic clasts (up 1 mm) and a second portion dominated by a fine-grained comminuted matrix with isolated silicate grains up to 0.5 mm. Pyroxene (Fs_14-58Wo_1-41) includes low- to high-FeO (Fs_14-58Wo_1-4) orthopyroxene and low-FeO augite (Fs_22-37Wo_32-41). A single plagioclase grain is An₉₁Or₁. The meteorite is a howardite.

Macroscopic Description: Kathleen McBride
The exterior of this flat, ordinary chondrite's surface is smooth and has a brown/black fusion crust with little dings and pits. This meteorite is very hard and dense. The interior is rusty and has a high concentration of metal.

Thin Section (, 2) Description: Tim McCoy and Linda Welzenbach
The section exhibits numerous well-defined chondrules (up to 2 mm) in a matrix of fine-grained silicates, metal and troilite. Moderate shock effects are present and weathering is extensive. Silicates are unequilibrated; olivines range from Fa_14-37, with a weak peak at Fa_21-25. Orthopyroxene range from Fs_10-22. The meteorite is an L3 chondrite (estimated subtype 3.6).

Macroscopic Description: Kathleen McBride
The exterior of these two meteorites have a thin, patchy, brown/black fusion crust. The exposed interiors are gray in color with a few visible clasts. The interior matrix is gray in color with numerous angular to sub-angular multicolored clasts.

Thin Section (, 2;, 4) Description: Tim McCoy and Linda Welzenbach

QUE 99033 Cross-Pol. Light	QUE 99058 Plane-Pol. Light	QUE 99058 Cross-Pol. Light

These meteorites are so similar that a single description suffices. The sections show a groundmass of comminuted pyroxene and plagioclase (up to 2.5 mm) with fine- to coarse-grained basaltic and pyroxenitic clasts ranging up to 2 mm. Both contain clasts similar in texture to the unusual eucrite ALHA81001. Pyroxenes include orthopyroxene (Fs_17-31Wo_0-4) and finely-exsolved pyroxenes that include augite (Fs₂₈Wo₃₇) and orthopyroxene. The Fe/Mn ratio of pyroxene is ~30. Plagioclase is An_70-95Or_0-2. The meteorites are howardites.

Macroscopic Description: Kathleen McBride
This carbonaceous chondrite has a dark gray to blackish crust, but appears to be a melted glob of chondrules spread over the entire exterior of the rock. The surface has a vesicular-like texture. The interior is charcoal gray with numerous mm-sized chondrules and light and dark gray crystalline materials. This meteorite is moderately hard and has a sulfurous odor.

Thin Section (, 2) Description: Tim McCoy and Linda Welzenbach
The section consist of a few small chondrules (up to 1.5 mm), mineral grains and CAIs set in a black matrix; rare metal and sulfide grains are present. Olivine compositions are Fa_1-39, with many Fa_0-3. The matrix consists dominantly of an Fe-rich serpentine. The meteorite is a CM2 chondrite.

Macroscopic Description: Kathleen McBride
20% of this achondrite's exterior is covered with a thin, black fusion crust. The interior is tan with tiny black inclusions <1 mm in size. Also visible are large (1 mm sized) euhedral olivine crystals.

Thin Section (, 3) Description: Tim McCoy and Linda Welzenbach
The section shows a groundmass of essentially monominerallic, coarse (up to 1.5 mm) comminuted orthopyroxene of uniform composition (Fs₂₁Wo₂). The Fe/Mn ratio of the pyroxene is ~30. The meteorite is a diogenite.

Macroscopic Description: Kathleen McBride
10% of the exterior surface of this achondrite is covered with thin brown/black patches of fusion crust. The meteorite is rusty, friable, and very fractured. The interior matrix has a rusty, sugary texture exhibiting elongated crystals, melted blebs and numerous inclusions.

Thin Section (, 4) Description: Tim McCoy and Linda Welzenbach

Reflected Light	Cross-Polarized Light	Cross-Polarized Light

The section consists of mm-sized enstatite grains (Fs_0-1), abundant SiO₂, metal, troilite, daubreelite, alabandite and schreibersite. The latter phases often occur as rounded enclaves in the enstatite. QUE 99059 is almost certainly paired with the trio QUE 94204/97348/97289, although it differs from them in having abundant SiO₂ instead of abundant feldspar. These meteorites are unusual aubrites or enstatite chondrite impact melt rocks.