The chemical formula of mineral Schorl is indicated by NaFe3(Al, Fe)6Si6O18(BO3)3(OH)4 or Sodium Iron Aluminum Boro-silicate Hydroxide. Schorl is actually a Silicate mineral. Schorl is usually used as mineral collection specimen and it is most commonly found exhibiting nice and splendid appearance when viewed with the aid of petrographic polarizing light microscopes used in the field optical mineralogy. It is also used as ornamental stone. It has also electrical uses. Schorl is actually considered as the most common mineral in the Tourmaline Group. It has been observed that all Tourmaline minerals are isostructural. In the field of optical mineralogy, isostructural means that the internal crystalline structure is the same. Schorl is usually found forming some very nice and classic tourmaline crystals that appear more splendidly exhibited when viewed with the aid of petrographic polarizing light microscope for mineralogists. Tourmaline crystals are really interesting because they are hemimorphic, having a different shaped top from the bottom of the crystal.
Long thin crystals of Schorl are most commonly found as inclusion in quartz crystals. This specimen is most often used as ornamental stone and is termed as tourmalinated quartz. When viewed with the aid of petrographic polarizing microscope, the unique long needle to straw sized, arrow straight, prismatic crystals of pitch black Schorl found criss-crossing the clear colorless quartz is more splendidly exhibited and found more fascinating. As the fact it is, Schorl is usually found colored black which can be also more interesting when viewed with the aid of polarized microscopes for mineralogists. Schorl is most commonly found showing vitreous to submetallic luster when viewed in reflected light of petrographic polarizing microscopes used in the field of optical mineralogy. Most crystals of mineral Schorl are found opaque in appearance. Schorl is also known to crystallize in the trigonal system of polarizing microscope.
The crystal habit of mineral Schorl as described in the field of optical mineralogy typically include elongated three sided prisms that appear more interesting when viewed with the aid of polarized microscopes used in optical mineralogy. It can be seen that the termination can be either a simple to complex trigonal pyramid or flat basal face. The prism faces are usually striated lengthwise. In cross-section, all tourmalines will appear predominantly triangular in shape. Doubly terminated crystals are hemimorphic. In the field of optical mineralogy, hemimorphic means that the two ends of the crystal are not exactly alike. Schorl can be also found massive in form. Schorl is most commonly found having absent cleavage although there is basal parting found when specimen is closely evaluated with the aid of polarized light microscope used in the field of optical mineralogy. Schorl is also showing uneven to conchoidal fracture when viewed with the aid of petrographic polarizing microscopes for mineralogists. The hardness measure of mineral Schorl when it is evaluated using the Mohs scale method ios usually 7 to 7.5. Schorl is most commonly found leaving a white streak when specimen is rubbed on a white porcelain streak plate. The specific gravity measure of the mineral is usually found 3.2+ grams per cubic centimeters, which is slightly heavier than average. Schorl is also known to be piezoelectric. The best field indicators of mineral Schorl usually includes overall triangular cross-section, hardness, crystal habit and color. Schorl is most commonly found associated with other minerals including those associated with granitic pegmatites and metamorphic rocks such as micas, quartz and feldspars. Schorl is sometimes regarded as a major component of igneous and metamorphic rocks. Despite the fact that being such rock type, it is the only black rock that form crystals with a clear triangular cross-section that can be seen more clearly visible when viewed with the aid of petrographic polarizing light microscopes. Schorl notably occurs at several localities including Germany, Brazil, England, Appalachian Mountains, Colorado and many others.
