Dolerite and Diabase.

I just ran across the word dolerite in the excellent science fiction novel Aurora by Kim Stanley Robinson (thanks, Songdog!), and of course I looked it up and found that it was sort of synonymous with diabase, both meaning ‘a dark, fine-grained igneous rock’ (you can see the gory details at the Wikipedia article: “Diabase is the preferred name in North America, yet dolerite is the preferred name in most of the rest of the world, where sometimes the name diabase is applied to altered dolerites and basalts. Many petrologists prefer the name microgabbro to avoid this confusion”), and since both words have interesting etymologies, I thought I’d post about them.

[French dolérite, from Greek doleros, deceitful (from its easily being mistaken for diorite), from dolos, trick; see del-2 in the Appendix of Indo-European roots.]

[From French diabase, originally meaning “diorite,” (now “basalt or gabbro lightly modified by metamorphism”), coined by French mineralogist Alexandre Brongniart (1770-1847), probably from Greek diabasis, a crossing over (from diabainein, to pass through or over; see DIABETES; the rock being so called because it is often found as intrusive sills and dikes in other rocks), or perhaps an alteration of an intended French *dibase (di-, two, from Greek di-; see DI-1 + base, basis, from Old French; see BASE1; the rock being so called in reference to feldspar and amphibole, two important constituent minerals of diorite).]


  1. And why exactly dolerite is hard to confuse with diorite. I guess, it was selected for easy confusion.

  2. Thinking back to the very brief period in which I was working in the Earth sciences, it seems like “dioritic” was much more common among the geologists than the noun form “diorite.”

  3. So, diabase is to dioritic as diabetes is to diuretic?

  4. The term diorite, and the commoner granodiorite, are used plenty, where the rocks themselves are plentiful.

    Prof. internet says, ‘In Great Britain the term “dolerite” was used … which has a meaning of a fresh-looking diabase and the term “diabase” itself was left to altered and old dolerites only.’

    In my recollection, dolerite feels old fashioned and imprecise in US geology.

    Here’s a slightly related question. Is there any context in which only one of the spellings grey / gray is used, on both sides of the Atlantic? A quick check shows that at least as far as horses and wastewater the answer is no.

  5. dolorite, dolomite, dolmen.

    I was expecting dol- had something to do with rocks. (Also ‘dolostone’, word derived from ‘dolomite’.)

    But no, each a separate etymology.

  6. Well, 돌 dol does mean ‘stone’ in Korean.

  7. Mongolian “chuluu” and Turkic “tash” are obviously related.

    Another win for the Altaic theory

  8. David Marjanović says:

    As usual, that’s only half-joking: the serious proposal is here. I really would like to know, though, why the “[c]ounterarguments against the etymology by Doerfer (TMN 2, 437-438) are not convincing” or what they are in the first place. (TMN is a book Türkische und mongolische Elemente im Neupersischen.)

  9. Michael Himmel says:

    Diabase reminded me immediately of adiabatic, which can refer to a process in which volume changes but heat doesn’t (because the heat does *not go through*).

  10. Plain “diabatic” for a process that does involve heat transfer also sees some use, but it is much less common than “adiabatic.”

  11. January First-of-May says:

    The two etymologies in the OP made me wonder about the etymology of microgabbro.

    I was not able to find anything on this specific term (which appears to be something along the lines of “small gabbro”.
    As for gabbro itself, it was apparently named (in the 18th century) for the small village of Gabbro, now in Rosignano Marittimo, Tuscany, Italy, where such rocks were found.
    The village name, in turn, is said to originate from an alteration of Latin glaber “smooth”, from PIE *gʰladʰ- (from *gʰel- ‎“to shine”‎); the English cognate is, of all things, glad (as in the word meaning “happy”).

  12. David Marjanović says:

    Fine-grained gabbro, I’m sure.

    PIE *gʰladʰ- (from *gʰel- ‎“to shine”‎)

    That’s a strange kind of ablaut. But wouldn’t syllabic *l, as in the zero-grade, become -la- in Latin anyway?

  13. The Problem is that the “a” is short. De Vaan reconstructs *ghlH2dh-ro-, and remarks: “Schrijver regards glaber as the phonetic outcome of the PIE preform, by a vocalization rule *CRHTC > *CRaTC. Since the usual reflex of *CRHC is *CRa:C, this may imply that the laryngeal was actually ousted before the putative allophonic prop vowel was phonologized. The acute accent of the BSl. forms points to the presence of a laryngeal.”.

Speak Your Mind