# CI chondrite

- Page: https://taslar.bumba.tr/en/stones/ci-chondrite/
- Turkish: CI kondrit
- Also known as: C1 chondrite, Ivuna-type carbonaceous chondrite
- Kind: Meteorite
- Classification: Meteorites and impact stones › Stony meteorites
- Hardness (Mohs): 2.5–7
- Specific gravity: 2.11 g/cm³
- Lustre: Dull
- Transparency: Opaque
- Colours: black, coal black, dark grey
- Composition: Over 90% by volume is fine-grained phyllosilicates (mainly serpentine–saponite intergrowths), with about 10% magnetite, 7% pyrrhotite, 5% carbonates and 5% ferrihydrite. It holds 18–20% water, 3–5% carbon (mostly organic matter) and 18–20% iron by weight; oxygen is the most abundant element (46%).
- Texture: A dark, fine-grained, clay-like matrix with no visible chondrules, calcium–aluminium-rich inclusions or amoeboid olivine aggregates. Porosity can reach 25–30%, and veins filled with sulfate minerals cut across it.
- Value ladder: 7/9 step, Precious stone

Black stones carrying the make-up of the Sun: watery, chondrule-free meteorites, the most primitive known.

CI chondrites (C1 or Ivuna-type carbonaceous chondrites) are a very rare group of carbonaceous chondrites, named after their type specimen, the Ivuna meteorite from Tanzania. They are the most chemically primitive meteorites known: their elemental composition, apart from gases, closely matches the Sun's. That makes them the standard reference for cosmic element abundances in planetary science. Orgueil, Alais, Ivuna, Tonk and Revelstoke are the known members of the group.

## How does it form?

CI chondrites come from an asteroid that formed at the start of the Solar System and never melted. On their parent body, liquid water seeped in through cracks and altered the rock almost completely: chondrules, calcium–aluminium-rich inclusions and olivine aggregates disappeared, replaced by clay-like water-bearing minerals. The water left veins filled with sulfate minerals in the cracks.

Despite this heavy alteration, CI chondrites have kept the Solar System's original elemental composition. Their oxygen isotopes clearly set them apart from other meteorite groups. Which asteroid is their parent body is still debated.

## What is it used for?

- **Cosmic element abundances:** They are the standard reference material for the composition of the Solar System.
- **Water and organic matter:** They help study how water and carbon compounds formed in the early Solar System.
- **Origin of life:** Their organic compounds are studied in debates on the origin of life's building blocks.

## Known CI chondrites

The known falls of this group are Orgueil (France, 1864), Alais (France, 1806), Ivuna (Tanzania), Tonk (India) and Revelstoke (Canada), together with CI-like specimens found in Antarctica. The largest and most studied is the 14-kilogram Orgueil.

## How to recognise it

- A coal-black stone made of a fine, clay-like matrix.
- Heavily altered by water, they contain no visible chondrules.
- Only laboratory study of its chemistry and oxygen isotopes can show that a stone is a CI chondrite.

## What determines its value?

CI chondrites are extremely rare: the number of known specimens is debated (between 5 and a little over 10), and their total known weight is about 17 kilograms. Their scientific value is very high, and their specimens are kept in museums and research institutions.

This information is educational, not buying, selling or investment advice. Value varies enormously with quality and treatment.

## Myths and misconceptions

- Myth: Carbonaceous chondrites are the most carbon-rich meteorites. Fact: CI chondrites hold the most carbon among carbonaceous chondrites (3–5% by weight), but some ureilites carry even more. The name “carbonaceous” was given to set them apart from the ordinary chondrites.

## Curious questions

**Why are CI chondrites so important?**

Although heavily altered by water, they have kept the Solar System's original elemental composition. That is why they are the standard reference material for element abundances in the Solar System. They also hold clues to the origin of volatiles and perhaps of life's building blocks.

## Did you know?

- They hold 18–20% water by weight, more than comet 67P/Churyumov–Gerasimenko.
- Ivuna and Orgueil contain ancient liquids trapped inside crystals, the only surviving direct samples of brines from the early Solar System.
- The Alais meteorite (France, 1806) was the first carbonaceous chondrite identified.

## Where is it found?

- Orgueil, Tarn-et-Garonne, France (Major deposit): The largest and most studied CI chondrite (14 kg), which fell on 14 May 1864.
- Alès (Alais), Gard, France (Historic source): Alais, which fell on 15 March 1806, was the first carbonaceous chondrite identified; 6 kg fell, but only 0.26 kg remains today.

## Sources

- [CI chondrite](https://en.wikipedia.org/wiki/CI_chondrite), Wikipedia
- [CI kondrit](https://tr.wikipedia.org/wiki/CI_kondrit), Vikipedi
- [Alais meteorite](https://en.wikipedia.org/wiki/Alais_meteorite), Wikipedia
- [Orgueil (meteorite)](https://en.wikipedia.org/wiki/Orgueil_(meteorite)), Wikipedia
- [Meteorite porosities and densities: a review of trends in the data (D. T. Britt & G. J. Consolmagno), Lunar and Planetary Science XXXV, abstract 2108](https://www.lpi.usra.edu/meetings/lpsc2004/pdf/2108.pdf), Lunar and Planetary Institute, 2004
- [Handbook of Mineralogy: Forsterite](https://www.handbookofmineralogy.org/pdfs/forsterite.pdf), Mineralogical Society of America


Source: https://taslar.bumba.tr/en/stones/ci-chondrite/ · Licence: CC BY-SA 4.0