Scapolite Gemstone Information

The prices, uses and value of Scapolite vary tremendously, depending on the size and quality of the gemstone. AJS Gems is your source for the highest quality colored stones from across the globe, available at Bangkok direct wholesale prices. Creating the finest jewelry starts with finding the best gemstones, and the best gemstones are found at AJS Gems.

Why Buy Loose Gemstones Instead of Pre-Set Jewelry?
 
There are many reasons, but basically it boils down to value and choice...

When buying your Scapolite gemstone loose instead of a pre-set stone, you can be sure you are getting the best value for your money.  Loose gemstones are less expensive, a better value, and you can really see what you are paying for.  The most important part of getting the right price and finding the best value is to first see what you're getting.  A jewelry setting will hide the inclusions inside a gem, and can deepen or brighten its color.  With a loose stone you can much more easily inspect the gem and see it for what it really is.  In this way you can get a better idea of its true worth and be sure you are paying a fair price.

The second advantage of buying a loose gemstone is choice.  You are free to pick the exact color, cut, shape and variety of the stone for the setting of your dreams, be it yellow gold, white gold, platinum or silver; prong set or bezel set with diamond accents.  You can experience the joy of creating your very own, one-of-a-kind jewelry design. Choose from a variety of jewelry settings and styles to create a completely original presentation that will perfectly suit your individual gemstone and will be as unique as you are!

                                                 

Scapolite is actually the name of a series between the sodium chloride rich mineral called marialite and the calcium carbonate rich mineral meionite. The structure of loose scapolite is similar to some feldspathoids in that it is composed of large open spaces in the framework of silicate and aluminum tetrahedrons. These open spaces are large enough to essentially cage the very large ionic groups of either Na4Cl or Ca4CO3. The sulfate ion shown in the formula is typically barely more than a trace, but is found in far greater percentages than the occasional fluorine or hydroxide interlopers in the scapolite structure.

Scapolite gems form in metamorphic rocks from the alteration of plagioclase feldspars. The entire scapolite series is analogous to the plagioclase series. If the formula of marialite is written as 3(Na(Al, Si)4O8)NaCl it is clear how well it matches the formula of the sodium rich plagioclase, albite, NaAlSi3O8. A similar look at meionite's formula, 3(Ca(Al, Si)4O8)CaCO3, shows that it too is near three times the formula of anorthite, CaAl2Si2O8. The addition of the extra sodium chloride or calcium carbonate occurs during metamorphism as well as substantial alteration of the structure. Although nearly pure albite and anorthite specimens are sometimes found, pure forms of meionite and marialite are unknown of in nature.

Distinguishing the scapolite crystals from each other is difficult as they differ only slightly in density and index of refraction, increasing in both with increasing calcium content. It is because of this closeness in properties and yet seemingly very different chemistries that scapolite has had its share of pseudonyms. Wernerite was the most common alternate name for the scapolite series, but now it has mostly disappeared from use. A few other names such as mizzonite and dipyre as well as marialite and meionite have been used as names for the entire scapolite series. Now scapolite is a name recognized by most every mineralogist and rock hound the world over.

Scapolite has a refractive index of 1.54 - 1.58 and a hardness of 6.5. The refractive index (RI), measured using a refractometer, is an indication of the amount light rays are bent by a mineral. Birefringence is the difference between the minimum and maximum RI. When birefringence is high, light rays reflect off different parts of the back of a stone causing an apparent doubling of the back facets when viewed through the front facet. 

Most gems have a crystalline structure. Crystals have planes of symmetry and are divided into seven symmetry systems. The number of axes, their length, and their angle to each other determine the system to which a crystal belongs.  Scapolite, which is Greek for "shaft", is commonly found in stubby to long prismatic crystals, hence the name. It is tetragonal so that it will commonly have a square or octahedral cross-section. It belongs to a rather exclusive symmetry class that is shared by only two other well known minerals, powellite and scheelite. The symmetry class is called the Tetragonal Dipyramidal Class and is characterized by only having the one primary four fold axis of rotation and a perpendicular mirror plane, denoted as 4/m. Unfortunately, scapolite rarely forms crystals with the complex faces that would be needed to see this unusual symmetry.

Color

Scapolite is usually found in colorless, white, yellow, green, pink and violet hues. The most sought after colors are shades of violet and blue.  The value increases with the darker colors. 

Cut

Scapolite is a metamorphic product, usually forming in hydrothermal metamorphic rocks.  Most Scapolite crystal mining occurs in Brazil, Madagascar, Switzerland and Burma.

According to their genesis the scapolite crystals fall naturally into four groups.

1. The scapolite limestones and contact metamorphic rocks. As silicates rich in calcium, it is to be expected that these minerals will be found where impure limestones have been crystallized by contact with an igneous magma. Even meionite (the variety richest in soda) occurs in this association, being principally obtained in small crystals lining cavities in ejected blocks of crystalline limestone at Vesuvius and the craters of the Eifel in Germany. Scapolite and wernerite are far more common at the contacts of limestone with intrusive masses. The minerals which accompany them are calcite, epidote, vesuvianite, garnet, wollastonite, diopside and amphibole. The scapolites are colorless, flesh-colored, grey or greenish; occasionally they are nearly black from the presence of very small enclosures of graphitic material. They are not in very perfect crystals, though sometimes incomplete octagonal sections are visible; the tetragonal cleavage, strong double refraction and uniaxial interference figure distinguish them readily from other minerals. Commonly they weather to micaceous aggregates, but sometimes an isotropic substance of unknown nature is seen replacing them. In crystalline limestones and calc-silicate rocks they occur in small and usually inconspicuous grains mingled with the other components of the rock. Large, nearly idiomorphic crystals are sometimes found in argillaceous rocks (altered calcareous shales) which have suffered thermal metamorphism. In the Pyrenees there are extensive outcrops of limestone which are penetrated by igneous rocks described as ophites (varieties of diabase) and iherzolites (peridotites). At the contacts scapolite occurs in a great number of places, both in the limestones and in the calcareous shales which accompany them. In some of these rocks large crystals of one of the scapolite minerals (an inch or two in length) occur, usually as octagonal prisms with imperfect terminations. In others the mineral is found in small irregular grains. It is sometimes clear, but often crowded with minute enclosures of augite, tourmaline, biotite and other minerals, such as constitute the surrounding matrix. From these districts also a black variety is well known, filled with minute graphitic enclosures, often exceedingly small and rendering the mineral nearly opaque. The names couzeranite and dipyre are often given to this kind of scapolite. Apparently the presence of chlorine in small quantities, which may often be detected in limestones, to some extent determines the formation of the mineral.

2. In many mafic igneous rocks, such as gabbro and diabase, scapolite replaces feldspar by a secondary or metasomatic process. Some Norwegian scapolite-gabbros (or diorite) examined microscopically furnish examples of every stage of the process. The chemical changes involved are really small, one of the most important being the assumption of a small amount of chlorine in the new molecule. Often the scapolite is seen spreading through the feldspar, portions being completely replaced, while others are still fresh and unaltered. The feldspar does not weather, but remains fresh, and the transformation resembles metamorphism rather than weathering. It is not a superficial process, but apparently takes place at some depth under pressure, and probably through the operation of solutions or vapours containing chlorides. The basic soda-lime feldspars (labradorite to anorthite) are those which undergo this type of alteration. Many instances of scapolitization have been described from the ophites (diabases) of the Pyrenees. In the unaltered state these are ophitic and consist of pyroxene enclosing lath-shaped plagioclase feldspars; the pyroxene is often changed to uralite. When the feldspar is replaced by scapolite the new mineral is fresh and clear, enclosing often small grains of hornblende. Extensive recrystallization often goes on, and the ultimate product is a spotted rock with white rounded patches of scapolite surrounded by granular aggregates of clear green hornblende: in fact the original structure disappears.

3. In Norway scapolite-hornblende rocks have long been known at Oedegrden and other localities. They have been called spotted gabbros, but usually do not contain feldspar, the white spots being entirely scapolite while the dark matrix enveloping them is an aggregate of green or brownish hornblende. In many features they bear a close resemblance to the scapolitized ophites of the Pyrenees. It has been suggrsted that the conversion of their original feldspar (for there can be no doubt that they were once gabbros, consisting of plagioclase and pyroxene) into scapolite is due to the percolation of chloride solutions along lines of weakness, or planes of solubility, filling cavities etched in the substance of the mineral. Subsequently the chlorides were absorbed, and pan passu the feldspar was transformed into scapolite. But it is found that in these gabbros there are veins of a chlorine-bearing apatite, which must have been deposited by gases or fluids ascending from below. This suggests that a pneumatolytic process has been at work, similar to that by which, around intrusions of granite, veins rich in tourmaline have been formed, and the surrounding rocks at the same time permeated by that mineral. In the composition of the active gases a striking difference is shown, for those which emanate from the granites are mainly fluorine and boron, while those which come from the gabbro are principally chlorine and phosphorus. In one case the feldspar is replaced by quartz and white mica (in greisen) or quartz and tourmaline (in schorl rocks); in the other case scapolite is the principal new product. The analogy is a very close one, and this theory receives much support from the fact that in Canada (at various places in Ottawa and Ontario) there are numerous valuable apatite vein deposits. They lie in basic rocks such as gabbro and pyroxenite, and these in the neighborhood of the veins have been extensively scapolitized, like the spotted gabbros of Norway.

4. In many parts of the world metamorphic rocks of gneissose character occur containing scapolite as an essential constituent. Their origin is often obscure, but it is probable that they are of two kinds. One series is essentially igneous (orthogneisses); usually they contain pale green pyroxene, a variable amount of feldspar, sphene, and iron oxides. Quartz, rutile, green hornblende and biotite are often present, while garnet occurs sometimes; hypersthene is rare. They occur along with other types of pyroxene gneiss, hornblende gneiss, amphibolites, etc. In many of them there is no reason to doubt that the scapolite is a primary mineral. Other scapolite gneisses equally metamorphic in aspect and structure appear to be sedimentary rocks. Many of them contain calcite or are very rich in calc-silicates (wollastonite, diopside, etc.), which suggests that they were originally impure limestones. The frequent association of this type with graphitic-schists and andalusite-schists makes this correlation in every way probable. Biotite is a common mineral in these rocks, which often contain also much quartz and alkali felspar.

Scapolite is a bright yellow green, golden green or violet  variety of olivine. It was originally found on Egypt's St. John's Island once known as Topazios, in the Red Sea, which is now known as Zeberget.