There is hope, though. If you wish to impress your friends with your ability to
distinguish amphiboles from pyroxenes in a hand specimens, look for the cleavage faces.
Pyroxenes as well as amphiboles have distinct cleavage planes, usually parallel to the
long axis of individual crystals. In pyroxenes the cleavages planes are approximately 92
degrees (and consequently app. 88 degrees, when seen from the other side) apart - they
appear to be at right angles. In amphiboles the cleavages planes are approximately 124
degrees (and consequently app. 56 degrees, when seen from the other side) apart - they
appear to be at distinctly blunt/pointed angles. Study the diagram and try to look at some
pieces, that are already identified to get a hang of it. The main point is getting used to
look at either the pointed or blunt angles, and realise they are complementary. Note that
it is often possible to discern the cleavage planes on the end of crystals, sometimes even
if they are undamaged.
The name 'pyroxene' is derived from the Greek 'pyr' meaning fire and 'xenos' a
stranger or alien, as it was believed not to be a primary mineral of volcanic rocks, that
are 'formed in fire'. Today we know this is wrong, and pyroxenes are known to be
abundant in lava and many other rocks. Pyroxenes are chemically very diverse and
many species have been described. Currently the following seem to be recognised as
species: €girine, Augite, Clinoenstatite, Clinoferrosilite, Diopside, Donpeacorite,
Enstatite, Esseneite, Ferrosilite, Hedenbergite, Jadeite, Jervisite, Johannsenite, Kanoite,
Kosmochlor, Namansilite, Natalyite, Omphacite, Petedunnite, Pigeonite, and
Spodumene. You may be familiar with some of them, others you may never see.
Pyroxenes often lead an obscure life, if any, in collections, but that should really be a
challenge to dedicated collectors. You can actually build a choice collection of excellent
specimens for a modest amount if you collect pyroxenes, and you may even be able to
find many yourself.
Pyroxenes are not used industrially, except as a component of rock for
construction, but many are used for gems. Spodumene (Kunzite and Hiddenite) comes as
very attractive pink, occasionally purple, and green stones. Cut Enstatite may show an
interesting optic 'Schiller' effect, and Hedenbergite and Diopside may either be
chatoyant or show asterism. Dark green chromian Diopside is cut to small faceted
stones, when clear, or to cabochons. Variously coloured Jadeite, Jade, has been cherished
as a gem and ornamental stone, chiefly in Asia, for centuries; note that only very little
'Jade' is Jadeite. Most 'Jade' used for jewellery and crafts is an amphibole, and every
now and then just about any green stone is passed of for 'Jade'.
€girine (named for €gir, god of the sea) produces very attractive crystallised
specimens, chiefly from the Malosa Complex (Malawi) and Mt. St. Hilaire (Quebec,
Canada), but most pyroxenes do produce very collectible specimens if you look for
them. You may have to wade through a lot of road material, but you will find very
worthwhile pyroxene specimens if you look for them. Pyroxenes are so abundant in
igneous, intrusive, and metamorphic rocks, that you will find them associated with
practically any mineral. €girine is one of the more abundant pyroxenes, and Our
records indicate that €girine from a range of deposits occurs on specimens that also
carry one or more of the following minerals: Aenigmatite, Albite, Analcime, Ancylite,
Andradite, Apatite, Arfvedsonite, Armstrongite, Astrophyllite, Baratovite,
Barytolamprophyllite, BastnŠsite, Batisite, Belovite-(Ce), Bertrandite, Beryllite,
Berzeliite, Biotite, Birnessite, Bornemanite, Brandtite, Braunite, Bustamite, Calcite,
Calcium-catapleiite, Canasite, Cancrinite, Catapleiite, Chalcocite, Chalcothallite,
Charoite, Chkalovite, Clinohedrite, Connellite, Copper, Cuprostibite, Dalyite,
Delhayelite, Diaspore, Digenite, Dolomite, Eckermannite, Ekanite, Elpidite,
Epididymite, Epistolite, Eudialyte, Eudidymite, Fedorite, Fenaksite, Ferro-hornblende,
Fluorite, Franklinite, Galena, Gerasimovskite, Goethite, Graphite, Hambergite,
Hardystonite, Hausmannite, Hedyphane, Hematite, Kalsilite, Kaolinite, Keldyshite,
Kogarkoite, Kupletskite, Kutnohorite, Lamprophyllite, Leucophanite, Lomonosovite,
Loparite, Lorenzenite, Lueshite, Långbanite, Låvenite, Macfallite,
Magnesiumastrophyllite, Magnetite, Malachite, Mangan-neptunite, Meliphanite,
Microcline, Miserite, Molybdenite, Monazite, Murmanite, Nadorite, Narsarsukite,
Natrolite, Natrosilite, Naujakasite, Nepheline, Neptunite, Nontronite, Opal, Orientite,
Orthoclase, Parakeldyshite, Paraumbite, Pectolite, Penkvilksite, Polylithionite,
Pyrochlore, Pyrophanite, Quartz, Raite, Rasvumite, Reedmergnerite, Rhabdophane,
Rhodonite, Richterite, Rinkite, Rosenbuschite, Rutile, Sarkinite, Searlesite, Semenovite,
Serandite, Shcherbakovite, Siderite, Sodalite, Sogdianite, Sorensenite, Sphalerite,
Steenstrupine, Stillwellite-(Ce), Strontium-apatite, Sugilite, Tausonite, Terskite,
Tetranatrolite, Thalcusite, Thomsonite, Thorosteenstrupine, Tinaksite, Titanite,
Tugtupite, Tuhualite, Tundrite, Tuperssuatsiaite, Turkestanite, Tvedalite, Ussingite,
Villiaumite, Vuonnemite, Willemite, Wšhlerite, Yuksporite, Zektzerite, Zircon,
Zirsinalite, and Zorite.
Specimen Handling
Pyroxenes are for all practical purposes stable in a normal household environment. They
are not harmed by light, changes in temperature in the normal comfort range, or known
to decompose. Pyroxene specimens can be fragile and should be handled with care like
any other mineral specimen. Pyroxenes are not appreciably soluble in water.
Bibliography
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This page is authored by Claus Hedegaard.
