UNAKITE

UNAKITE

 
 

A. Unakite polished paper weight (width - 6.7 cm) from the type area in the Unaka range of the Southern Blue Ridge Province near the Tennessee-North Carolina line.  This piece was given to me by my dear friend Anna Jonas Stose (1881-1974), who mapped the geology of much of the southern Blue Ridge Province.  R.V. Dietrich collection. (© photo by Dick Dietrich)

B. Unakite.   Polished gemstones (large cabochon, greater axis - 3.7 cm) fashioned from material from Augusta County, Virginia.  This material  has a so-to-speak intermediate grain size and contains more epidote per unit volume than the specimen shown in "A."  As indicated by the faceted stones (upper left and right), some masses of alkali feldspar and epidote within the rock from this locality (and from several other localities!) are large enough to yield cut stones that consist wholly, or nearly so, of only epidote or alkali feldspar.  The small cabachons are arranged to show different percentages of the two constituents -- left to right the feldspar content decreases as the epidote content increases.   
R.V. Dietrich collection. (© photo by Dick Dietrich)

DESCRIPTIONs: Although unakite is frequently and widely referred to as an epidotized granite (which seems to be the origin of the type locality rock and those shown in Figures A & B), many items labeled unakite in the market place have quite different origins and overall compositions.   Indeed, several so-labeled marketplace items consist largely of an alkali feldspar and epidote with little if any quartz, a specific constituent of granite.  Properties of the typical feldspar of these rocks -- i.e., deep salmon colored alkali feldspar -- and of quartz  (typically nearly colorless and commonly microcrystalline) are given under the Description subheading in the GRANITE entry.  Properties of epidote, as it occurs in these rocks, AND a general description of the rocks called unakite follow:

  Epidote Ca2(Fe,Al)Al2(Si2O7)(SiO4)O(OH):
    Color - mixture of pistachio (bilious, to me) yellowish green
    H.   6
    S.G.  3.4 - 3.48
    Light transmission -  opaque
    Luster
-  pearly to subvitreous
    Breakage -  irregular
    Miscellaneous - typically massive -- i.e., finely crystalline.

  Unakite:

    Color - mixture of pistachio (bilious, to me) yellowish green (epidote) and salmon pink (feldspar) plus or minus nearly colorless (quartz)
    H. (effective hardness)  6 - 7
    S.G.  2.55 - 2.85
    Light transmission -  opaque
    Luster
-  pearly to subvitreous, depending upon  percentages of constituents and what part(s) of the rock's surface is viewed
    Breakage -  highly irregular
    Miscellaneous - color mixture is distinctive;  epidote occurs as veinlike masses as well as fairly discrete grains, most of which consist of massive material, in some of these rocks;  the feldspar in some of these rocks appears to be partially epidotized;  the rock at some localities is foliated, in some places an augen gneiss.

OTHER NAME:

USES: Beads (tumbled pieces as well as spheres and other fashioned shapes);  tumbled chips, cabochons, faceted, freeforms and scarabs for jewelry -- in particular for relatively large pieces in which one can see the contrasting green and pink constituents to best advantage, but also in rings;  eggs, spheres, pyramids, hearts, wands and palmstones;  carvings, both small for such things as pendants and larger for curios;  small boxes and other containers;  paperweights; etc.  Some unakite has been used as tile  -- e.g., on  the  main terrace of the National Museum of Natural History (Smithsonian Institution) in Washington, D.C. 

OCCURRENCES: Unakite per se occurs as parts of granitic masses -- commonly small masses such as dikes and lenses -- that have undergone epidotization, with the epidote representing diverse alteration and/or replacement processes;  it also as cobbles and pebbles in unconsolidated sediments derived at least in part from such masses.  The above described virtually quartz-free unakite-like rocks have, I suspect,  several diverse origins, none of which I have seen described well enough professional publications to warrant summarizing herein.
 
NOTEWORTHY LOCALITIES: Epidotized rocks are relatively common.  Unakite and unakite-like rocks have been recovered from several places in the Blue Ridge Province of the eastern United States -- e.g., in Madison (e.g., near Bluff) and Mitchell counties, North Carolina; Unicoi County, Tennessee; and Augusta and Roanoke counties, Virginia.  I have seen several pebbles, cobbles, and boulders of similar rocks in glacial drift and along Great Lake beaches in, for example, Michigan. On the basis of personal observations of many Blue Ridge occurrences and several cobbles (etc.) in unconsolidated materials of the upper midwestern states, I consider some of the material from the Airpoint granite  of Roanoke County, Virginia to be top-grade gemrock rough, with rocks from none of the other listed localities -- including the type area in Madison County, North Carolina -- to be even close seconds so far as the quality one would like to
use as gemrock rough.   I realize, however, that several will not agree with my evaluation, AND, my statement does not, of course, refer to occurrences elsewhere in the world or even to those in the Blue Ridge Province of the eastern United States that I have not visited. For example, I have not, so far as I know, seen specimens or things fashioned from the localities the localities recorded on the www.ontariominerals.com/ontario_lapidary web site: "The feldspar-epidote mixture known as 'unakite' is found at the Canada Radium Mine; what is apparently the same mixture, [but] given the name "mylonite", is mentioned from Monk Road, Bancroft, by Leach, 1964, p.9 [see Appendix C]. [and] David Millis (1999) mentions the feldspar-epidote combination 'unakite', fine cutting material with good color, from the Marmora Quarry, near Madoc [,Ontario, Canada]." 

Although much of the unakite-like material marketed as unakite is said to come from Brazil, China and South Africa, I have been unable to find well documented reports that give any localities other than
Upinton and Neilersdrif, Northern Cape Province, South Africa.

REMARKS: Unakite was named for occurrences in the Unaka range of the Great Smoky region in the Blue Ridge province of eastern Tennessee and western North Carolina by Bradley (1874), who called it "Unakyte, an epidotic rock."  (I suspect his Bradley's use of the -yte suffix, rather than the -ite suffix was in deference to J.D. Dana's suggestion that such could be used to distinguish rock names from mineral names.)   However, as mentioned under the DESCRIPTION subheading, this designation has been extended (dishonored?) -- especially in the market place -- to include several rocks that are characterized by deep salmon colored feldspar and green epidote but contain little, if any, quartz.  Although I would prefer that these virtually quartz-free rocks be called unakite-like or, at least, "unakite," I feel sure this will not come to pass. So, it seems that we shall have to live with unakites and unakites that differ from accepted nomenclature usage. 

Along this line, two other rocks -- okkolite and an otherwise unnamed epidote-quartz rock -- seem noteworthy here:  1.Okkolite, apparently made up largely of diversely colored epidote grains, is from near Keimoes, Cape of Good Hope Province, South Africa, where it has been used as a gemrock.   2.The epidote-quartz rock, is said to be from Sonora, Mexico and  to have been fashioned into some fine cabochons.   Both of these gemrocks are likely epidosites -- i.e., rocks made up largely of epidote, as the major component, and quartz.  And, I suspect that at least the one from Mexico might resemble stones fashioned from epidote-rich portions of unakite (e.g., the faceted one in the upper right of Figure B).  Indeed, one wonders if either, or both, of these rocks is spatially associated with unakite:  Epidosite and unakite have been found so related near Fisher's Gap, in the Blue Ridge Povince of Madison County, Virginia (Phalen, 1903).

A lesson for collectors:  I still bear a scar from a deep cut and loss of much blood suffered from a small flying disc broken from a student's apparently improperly tempered hammer while she was trying to get a good sample of unakite from the Airpoint mass southwest of Roanoke, Virginia.  Indeed, several years later, an operation was necessary to remove the metal disc. The important aspect of this story is that several good samples were loose on the ground adjacent to the exposure, just so-to-speak waiting to be collected -- i.e. no hammering was required to get good specimens.  So, I mention this episode to emphasize two things:  1.Fine specimens are often loose, and thus readily available, near outcrops and road cuts.  and  2.One should always be extremely careful when using hammers, chisels, and other tools to remove rocks from exposures or,  I should add, even when breaking pieces of loose rubble.

According to information supplied me by those familiar with efforts to establish official state minerals, rocks, and gemstones for Virginia,  listings of unakite as the state gemstone of Virginia (e.g., on the web site  www.jackgolightly.com) are erroneous.  And, I suspect the same can be said about listings of unakite as the "official stone"  for South Carolina  (e.g., on web site wwwdesigner.cabs.com). 

SIMULANTS:  None that I have seen or seen described.

REFERENCES: No general reference. VanLandingham, 1962, pts.3 & 4; Owens, 1977.  

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Last update:  8 July 2013
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