Post by MyNewHobby on Aug 8, 2009 16:11:53 GMT -5
Unakite can be a combination of Epidote, Feldspar, and in some cases clear quartz.
This rock has a mohs (hardness) of 6.5 - 7. This is not a solid 6.5 - 7 due to it being a combination rock.
I got the following from Central Michigan University's College of Science and Technology.
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The Epidote ...
Color - mixture of pistachio (bilious, to me) yellowish green
Hardness 6
Specific gravity 3.4 - 3.48
Light transmission - opaque
Luster - pearly to subvitreous
Breakage - irregular
Miscellaneous - typically massive -- i.e., finely crystalline.
The Unakite ...
Color - mixture of pistachio (bilious, to me) yellowish green (epidote) and salmon pink (feldspar) plus or minus nearly colorless (quartz)
Hardness (effective hardness) 6 - 7
Specific Gravity 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.
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.
This rock has a mohs (hardness) of 6.5 - 7. This is not a solid 6.5 - 7 due to it being a combination rock.
I got the following from Central Michigan University's College of Science and Technology.
_________________________________________________
The Epidote ...
Color - mixture of pistachio (bilious, to me) yellowish green
Hardness 6
Specific gravity 3.4 - 3.48
Light transmission - opaque
Luster - pearly to subvitreous
Breakage - irregular
Miscellaneous - typically massive -- i.e., finely crystalline.
The Unakite ...
Color - mixture of pistachio (bilious, to me) yellowish green (epidote) and salmon pink (feldspar) plus or minus nearly colorless (quartz)
Hardness (effective hardness) 6 - 7
Specific Gravity 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.
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.