Proposed Required Classification Elements for Each Meteorite Type

Classification Handbook for the Meteoritical Society Nomenclature Committee
DRAFT Apr. 2011


Nomenclature Notes and Abbreviations

Additional information, links, and photographs are available at:

Abbreviations and Nomenclature Notes


AUBRITES

Minerals and compositions:

Mineral Modes (vol%): N/R

Texture:


ACAPULCOITE-LODRANITE Family

Minerals and compositions:

Mineral Modes (vol%): N/R

Texture:


BRACHINITES

Minerals and compositions:

Mineral modes (vol%):

Texture:


CARBONACEOUS CHONDRITES (CI, CM, CO, CV, CK, CR, and CH)

Minerals and compositions:

Mineral modes (vol%): N/R

Texture: N/R

Petrologic types:


CB CARBONACEOUS CHONDRITE

CBa and CBb chondrites (Bencubbin-like)

Minerals and compositions:

Mineral Modes (vol%): N/R

Texture:


ENSTATITE CHONDRITES

EH and EL chondrites

Minerals and compositions:

Mineral modes (vol%): N/R

Texture:


HED CLAN (Howardites, Eucrites, and Diogenites)

Eucrites (basaltic and “cumulate” types)

Basaltic eucrites are typically brecciated (monomict or polymict). Either orthopyroxene or pigeonite will be present.

Minerals and compositions:

Mineral Modes (vol%): N/R

Texture:

Diogenites

Minerals and compositions:

Mineral Modes (vol%): N/R

Texture:

Howardites

Howardites do not have unique mineral characteristics like other meteorite classes and are considered to be regolith breccias that consist essentially of >10 modal % of diogenites and <90 modal % of eucrites, some of which are very dark, shock-melted clasts. If a suspected howardite contains <10 modal % of diogenite and >90 % eucrite material the stone is classified as a eucrite. On the other hand, a stone that is <10 % eucrite and >90 % diogenite, it is a diogenite. Howardites may also contain minor components that include carbonaceous chondrites, in addition to minor exotic clasts.


ORDINARY CHONDRITES (H, L, and LL)

Equilbrated Chondrites

Minerals and compositions:

Mineral modes (vol%): N/R

Texture: N/R

Shock level:

Weathering grade:

Unequilibrated Chondrites – Petrologic types

CriterionPetrologic Type
3 4 5 6
Homogeneity (% mean deviation)px ≥5%; olivine ≥5%

<5% to homogeneoushomogeneous
Low-Ca pyroxenepredominately monoclinic>20% monoclinic<20% monoclinicorthorhombic
Feldsparminor primarysecondary, <2µm grainssecondary, 2-50µm grainssecondary, >50µm grains
Chondrule glassclear, isotropicdevitrifiedabsent
Matrixopaque to transparenttransparent microcrystallinerecrystallized
Chondrule-matrix boundarysharply definedmoderately diffusediffuse

STONY-IRON METEROITES

Mesosiderites

Minerals and compositions:

Mineral Modes (vol%):

Texture:

Pallasites

Minerals and compositions:


RUMURUTI (R Class)

Minerals and Compositions:

Mineral Modes (vol%): N/R


UREILITES

Minerals and compositions:

Mineral Modes (vol%): N/R

Texture:


WINONAITES

Minerals and compositions:

Texture: