L chondrite

L chondrite
— Group —
NWA 869, an L4-6 chondrite
Type	Chondrite
Structural classification	?
Class	Ordinary chondrite
Subgroups	L3 etc
Parent body	Possibly 433 Eros, 8 Flora or the Flora family as a whole
Composition	Olivine (characteristic fayalite (Fa) of 21 to 25 mol%), hypersthene (an orthopyroxene), iron–nickel 4–10%, troilite, chromite, Na-rich feldspar, Ca-phosphates
Petrologic type	6 (>60%)
Alternative names	L chondrite meteorites, Hypersthene chondrites, Olivine hypersthene chondrites
Walters, an L6 chondrite

The L type ordinary chondrites are the second most common group of meteorites, accounting for approximately 35% of all those catalogued, and 40% of the ordinary chondrites. The ordinary chondrites are thought to have originated from three parent asteroids, with the fragments making up the H chondrite, L chondrite and LL chondrite groups respectively.

Their name comes from their relatively low iron abundance, with respect to the H chondrites, which are about 20–25% iron by weight.

Historically, the L chondrites have been named hypersthene chondrites or olivine hypersthene chondrites for the dominant minerals, but these terms are now obsolete.

Characteristic is the fayalite content (Fa) in olivine of 21 to 25 mol%. About 4–10% iron–nickel is found as a free metal, making these meteorites magnetic, but not as strongly as the H chondrites.

The most abundant minerals are olivine and hypersthene (an orthopyroxene), as well as iron–nickel and troilite. Chromite, sodium-rich feldspar and calcium phosphates occur in minor amounts. Petrologic type 6 dominates, with over 60% of the L chondrites falling into this class. This indicates that the parent body was sizeable enough (greater than 100 kilometres (62 mi) in diameter) to experience strong heating.

Many of the L chondrite meteors may have their origin in the Ordovician meteor event. Compared to other chondrites, a large proportion of the L chondrites have been heavily shocked, which is taken to imply that the parent body was catastrophically disrupted by a large impact. This event has been radioisotope dated to around 470±6 million years ago.