Kolang        1°53’18.8"N, 98°39’39.6"E

Sumatera Utara, Indonesia

Fall: 1 Aug 2020

Classification: Carbonaceous chondrite (CM1/2)

History: (M. Farmer, Arizona) Around 4 pm local time (9 am UTC) on 1 August 2020, residents in northwest Sumatra (Central Tapanuli Regency) heard loud booming sounds that shook their houses. A single stone weighing ~2100 g went through the roof of a house in Kolang at 1°53’18.8"N 98°39’39.6"E (Satahi Nauli, Kolang, Central Tapanuli Regency, North Sumatra, Indonesia) and embedded itself into the soil beside the house. Another stone impacted in a rice paddy about 2.2 km south of the main mass. Two more stones were found ~7.8 km to the SE (around 1°49’50.22"N 98°41’51.22"E). Michael Farmer initially acquired 266 g, which includes fragments from the main mass and the rice paddy stone. This material was used for the classification.

Physical characteristics: To date, four stones have been recovered 2100 g (main mass), ~250 g (rice paddy), ~100 g (in two pieces), and ~100 g (complete stone). The masses of the two 100 g stones were estimated from their photographs. The main mass is blocky with a flat face and well-developed regmaglypts. About 250 g was broken off the main mass revealing a highly brecciated interior. Fragments crushed with water emit a delicate, earthy smell, though not as persistent or complex as that from Aguas Zarcas or Murchison.

Petrography: (L. Garvie, ASU) The interior of the stones are dark gray to black and sparsely decorated with light-colored speckles, and host common breccia fragments that protrude from the fracture surfaces. One fragment shows a large (3 mm) CAI with a pinkish hue. Three breccia types are visible: hard with conchoidal fracture and lacking or poor in chondrules; chondrule rich; and, greenish gray. Powder XRD shows considerable mineralogical diversity between different areas of matrix and clasts. Representative pieces from the bulk matrix are dominated by serpentine, with medium- to low-intensity reflections for regularly interstratified tochilinite/cronstedtite, tochilinite, calcite, pyrrhotite, and pentlandite. Some areas contain two distinct serpentines with basal spacings of 7.297 and 7.213 Å. BSE images from an ~1.5 × 2 cm fragment from the visually average lithology shows intense brecciation at all magnification scales, but is best described by two end-member petrographies. A) Intensely comminuted consisting of breccia fragments, sparse silicate fragments, and rare recognizable chondrules in a fine-grained matrix that is locally PCP rich. The chondrules and silicate fragments show a range of alteration to hydrous phases and many lack anhydrous silicates. B) Chondrule-rich breccia clast with a matrix dominated by PCP-rich objects. Chondrule mean diameter=125 μm (n=41, range 34 to 291 μm), not including a large 1.5 × 1 mm BO chondrule. Particularly noticeable in hand specimen are sparsely distributed greenish-gray breccia clasts (to 2 cm). Powder XRD shows the clast to be dominated by two serpentines, pyrrhotite, pentlandite, and calcite, and a medium-intensity basal reflection from well-crystallized smectite. Polished mount of this clast shows abundant chondrule pseudomorphs and coarse-grained sulfides.

Geochemistry: Oxygen isotopes (K. Ziegler, UNM) (linearized, all per mil, TFL slope=0.528): Eight fragments were analyzed by laser fluorination of which seven lie within the CM field. Two pieces were run from each fragment. Sample weights for each measurement were between 2.0 and 5.6 mg. All data in ‰. These include: Average lithology fragment 1 (δ¹⁸O 7.669, δ¹⁷O 1.332, Δ¹⁷O -2.717 and δ¹⁸O 8.591, δ¹⁷O 1.493, D18O -3.043); Average lithology fragment 2 (δ¹⁸O 9.141, δ¹⁷O 2.171, Δ¹⁷O -2.656 and δ¹⁸O 8.477, δ¹⁷O 1.992, Δ¹⁷O -2.484); Chondrule-rich lithology (δ¹⁸O 7.310, δ¹⁷O 1.480, Δ¹⁷O -2.380 and δ¹⁸O 9.245, δ¹⁷O 2.224, Δ¹⁷O -2.658); Chondrule-poor clast 1 (δ¹⁸O 11.378, δ¹⁷O 2.708, Δ¹⁷O -3.299 and δ¹⁸O 11.137, δ¹⁷O 2.580, Δ¹⁷O -3.301); Chondrule-poor clast 2 (δ¹⁸O 8.774, δ¹⁷O 2.116, Δ¹⁷O -2.517 and δ¹⁸O 9.765, δ¹⁷O 2.414, Δ¹⁷O -2.742), Chondrule-poor clast 3 (δ¹⁸O 13.133, δ¹⁷O 3.984, Δ¹⁷O -2.950 and δ¹⁸O 12.346, δ¹⁷O 3.310, Δ¹⁷O -3.209). Greenish-grey breccia clast (δ¹⁸O 6.377, δ¹⁷O 0.642, Δ¹⁷O -2.725 and δ¹⁸O 6.790, δ¹⁷O 0.848, Δ¹⁷O -2.737). The data for the metal-rich and chondrule-rich clast falls outside the CM field (δ¹⁸O -0.161, δ¹⁷O -6.189, Δ¹⁷O -6.104 and δ¹⁸O 1.595, δ¹⁷O -4.374, Δ¹⁷O -5.216). Microprobe (L. Garvie, ASU): Olivine shows a wide compositional range from Fa_0.5 to Fa_41.5 (n=13), with CaO up to 0.5 wt%, Cr₂O₃ up to 0.6 wt%, NiO up to 0.1 wt%, and Al₂O₃ up to 0.5 wt%.

Classification: CM1/2. All the oxygen isotopes, except the metal- and chondrule-rich clast, fall within the CM field. The dominant lithology contains areas with chondrules completely replaced by hydrous silicates and intimately associated and mixed with chondrules and olivine fragments partially replaced by hydrous phases (CM1/2), to areas more typical of CM2 meteorites. The bulk mineralogy is largely consistent with CM1 to 2 meteorites.

Specimens: Total known weight of approximately 2550 g. The distribution of the masses are as follows Michael Farmer (296 g); ASU 28.7 g off the main mass; remaining main mass of 1843 g was purchased by Robert Wesel, Mark Lyon and Jared Collins and now owned by Jay Piatek. The whereabouts of the two smaller stones is unknown.