from The American Heritage® Dictionary of the English Language, 5th Edition.
- noun Tourmaline, especially black tourmaline.
from The Century Dictionary.
- noun A term used by early mineralogists to embrace a large group of crystallized minerals: later limited to common black tourmalin.
from the GNU version of the Collaborative International Dictionary of English.
- noun (Min.) Black tourmaline.
from Wiktionary, Creative Commons Attribution/Share-Alike License.
- noun mineralogy The most
common varietyof tourmaline.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- noun black tourmaline
from The American Heritage® Dictionary of the English Language, 4th Edition
The lowest range above Djidda is calcareous; but its rocks soon change into gneiss, and a species of granite, with schorl in the place of feldspath, accompanied by predominant masses of quartz, and some mica.
Structurally, therefore, these isles are a continuation of Land's End, but the granite has become less consistent and more friable; it is largely broken into felspar, quartz, and mica, with schorl, chlorite, and hornblende.
Numerous other minerals are at times mistaken for tin, the most common of which are tourmaline or schorl, garnet, wolfram (which is a tungstate of iron with manganese), rutile or titanic acid, blackjack or zinc blende, together with magnetic, titanic, and specular iron in fine grains.
This is more especially true of chlorite, schorl, hornblende and augite.
Roche hermitage in Cornwall occupies a spire of rocks of schorl that shoots 100 feet above the surrounding moor.
The granite is dark red, often inclosing veins of quartz, crystallized and compact, and likewise well-formed crystals of schorl.
If the stuff does not answer the magnet, it is probably schorl (tourmaline), hornblende, or dark quartz.
I observed neither hornblende, black schorl, nor rutile titanite, in this granite.
I saw distinctly that, wherever they crossed each other, the veins containing mica and black schorl traversed and drove out of their direction those which contained only white quartz and feldspar.
We are ignorant of the extent of the cavities which subterranean fires and volcanic agitations may have produced in the bowels of the earth in those primitive rocks, which, containing considerable quantities of amphibole, mica, garnet, magnetic iron-stone, and red schorl (titanite), appear to be anterior to granite.