If you have spent any time viewing any of my websites you know that I have a passion for BaTiSi 3 O 9 also known as Benitoite. Though benitoite has been found in a few other locations in the world (in Arkansas, USA and in Japan and Australia), so far, the only gem-quality specimens have been found in California. Rare orange heat-treated specimens are known. The last two minerals are either visible on the drusy surface of the natrolite or are completely covered by natrolite. The mine has gone by many names over it's 106 year history. Hardness: is 6 – 6.5 The hornblende occurs in minute needles, felted masses of needles, blades, and stouter prisms. The hardness is between 5 and 6 and the specific gravity 3.18 to 3.19. Benitoite is usually found in association with other rare minerals, which include natrolite, joaquinite and neptunite. Intense blue fluorescence under short-wave ultraviolet light. Originally, Couch assumed that the mineral was a corundum mineral called sapphire because of its color similarity. Such a low dip would account for the failure of the incline to cut the mineralized zone. The spheroidal shape of the blocks and the open spaces between them were doubtless formed by decomposition and leaching along fracture planes. The minerals Albite, joaquinite, natrolite, neptunite and serpentine occur mainly with this. The crystals are about 2 centimeters in length and the plate measures about 15 x 11 x 2 centimeters in size. Benitite was designated the official staple in 1985 by California. Faceted benitoite: Three blue stones of faceted benitoite. Many of the crystals are naturally etched on one or more sets of faces. Rock hounds, gem and specimen hunters, this is your chance to find one of the rarest and most desirable gemstones in the world! The precious rock is used to produce jewellery as a gemstone. The failure might also be due to the pinching out of the vein a short distance below the large pocket opened in the "glory hole." Other minerals occurring in smaller quantity in the cavities are emerald-green copper stain, amphibole needles, albite, aegirine, and psilomelane. The benitoite mine is in the southeastern part of San Benito County, near the Fresno County line. Benitoite for sale at wholesale prices. The mine is in the end of one of the branching ridges from the south side of Santa Rita Peak. This locality was for years the only one from which this species was taken. After 100 years, the Benitoite Gem Mine is finally open and offering field trips to the public. The vast majority of crossite included are floaters with complete terminations on … The natrolite, with which the benitoite and neptunite are associated, does not generally occur in distinct crystals of any size. It forms massive granular white aggregates of crystallized material with curved ridge-like or cockscomb-like groups of crystals and drusy botryoidal masses in the cavities. These have a bluish to yellowish green to nearly colorless pleochroism, and are in part probably actinolite and in part glaucophane or allied hornblende. Color: is typically blue, but also colorless and yellowish. The prospect tunnel cut through the hornblende schist formation into decomposed serpentine. Benito has a deep blue color scheme and wears either the winter or summer uniform depending on the season. They are composed of one or more varieties of hornblende, some partially chloritized, with albite, and, near the vein, with natrolite. Jointing of the rock and the irregular nature of the vein, however, make accurate measurements difficult. Benitoite has a specific gravity of 3.65, compared to a specific gravity of 3.9 to 4.1 for sapphire. Mined at Benitoite Gem Mine San Benito California. The California State Gemstone, Benitoite. The incline shaft was sunk 35 feet deep from the north side of the open cut at about the middle. Benitoite is one of the rarest gemstones in the world. Doctor Louderback mentions the outcrop of spheroidal gabbro on the southeast of the benitoite deposit on the hillside. The rock is therefore a partly metamorphosed diabase or gabbro. Benitoite Engagement Ring, Rare American Gemstone, Handmade, shaped amd formed, rarest stone found in Cali USA, Handcrafted Gift For Her TamaraMJewelry From shop TamaraMJewelry Slabs of bluish hornblende rock with a drusy pure white crust of natrolite containing brilliant reddish-black neptunite and blue benitoite in fine crystals are excellent for the same purpose. Neptunite is titanium silicate containing iron, manganese, potassium, sodium, and magnesium. Benitoite has been found in bowlders a few hundred yards west of the mine on the hillside and in the creek. When viewed perpendicular to the vertical axis with a dichroscope the twin colors or two rays of light are very intense to pale blue (depending on the depth of color of the crystal) and colorless. Vein material formed the roof of the prospect tunnel for several feet near its mouth. Very light and very dark rocks lie at the lower end of the price continuum. Benitoite has never been found in quantity or as crystals much larger than 5cm across. Such faces are a little dulled or slightly pitted. Benitoite fluoresces under short wave ultraviolet light, appearing bright blue to bluish white in color. Public domain photo by Parent GÃ©ry. 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The smaller open cut exposed vein material with benitoite, which was more plentiful near the east end of the cut than at the west end. The Mineral in Japan occurs on a dike cutting a serpentinite body of magnesio-riebeckite-quartz-phlogopite. An excellent description of the new California gem mineral, benitoite, has recently been given by G. D. Louderback, of the University of California. The unfilled cavities and seams in the vein zone aided by later fractures and faults has offered an easy passage for more recent decomposing meteoric waters. Most benitoite deposits have been found in California, particularly in San Benito County, and in Arkansas and Japan. These flashes of colored lights along with the natural fine blue of benitoite render the gem particularly beautiful. The benitoite deposit occurs in a large area of serpentine which extends many miles northward past the New Idria quicksilver mine and a few miles southward, and forms the summit of an anticlinal ridge pitching down to Coalinga. The neptunite is subject to the same relations with the natrolite and is, in places, partly surrounded by benitoite. It was discovered about halfway between San Francisco and Los Angeles by prospector James M. Couch in the San Benito Mountains in 1907. The intensity of the blue diminishes as the light ray penetrates the crystal at other angles until perpendicular to the base, when the crystal is colorless. It is an extremely rare titanium cyclosilicate blue barium found in serpentinite that has been altered hydrothermally. The amphiboles are actinolite, a variety intermediate between crossite and crocidolite, and a little glaucophane. It is evident that J. M. Couch, of Coalinga, grubstaked by R. W. Dallas, was instrumental in finding the deposit. When viewed parallel to the vertical axis, or perpendicular to the base, the two rays are colorless and remain so while the dichroscope is rotated. It has been correctly identified in Montana, Arkansas, Japan, and Australia even though they have evolved under slightly different conditions and are only increasing large enough to be considered a mineral accessory. Transparency: Crystals are transparent to translucent. Ancient drop of water rewrites Earth’s history, Newly discovered baby Titanosaur sheds light on dinosaurs’ early lives, Long-gone bacteria blows the whistle on gold deposits, When Britain was fringed by tropical seas, Tsunami unleashed by Anak Krakatoa eruption was at least 100m high. How is Benitoite formed? In 1985 benitoite was designated as the official state gem of California. The chemical analyses show it to be an acid barium titano-silicate corresponding to the formula BaTiSi3O9 . After the type locality, "as it occurs near the head waters of the San Benito River in San Benito County", California, USA. Rock hounds, gem and specimen hunters, this is your chance to find one of the rarest and most desirable gemstones in the world! On a chemical level, it is classified as a barium titanium silicate mineral. Benitoite is named after San Benito County, California where it was discovered in 1907 (The locality is at the very southern tip of San Benito County. While the mineral benitoite itself is quite rare, large gem-grade crystals have only been found in one very small region of California, and in commercial quantities only on one small hill in San Benito County. Neptunite is practically insoluble in hydrochloric acid. Deeper colored stones may be cut in the same way or with the table in an intermediate position, if the color is very strong. This schist inclusion has been described by Kalph Arnold as 150 feet wide at its widest point and at least 1,200 feet long. Tabular dipyramidal crystals. Virtually all collectors specimens for this mineral are from this area. In the cavities the natrolite occurs in simple well-developed white columnar crystals up to a centimeter or more in thickness and several times as long. The California State Gemstone, Benitoite. The metamorphism of the schist inclusion has been of two kinds â first mashing and sheeting of the original basic rock producing schistosity and opening channels for solutions and then a passage of mineral-bearing solutions recrystallizing and replacing the minerals of the rock with albite. See more ideas about benitoite, rocks and minerals, gems and minerals. The natrolite did not permeate far into the rock, but formed a coating on the walls of the fissures. This occurs in low temperature, high-pressure conditions typical of subduction zones at the edge of the converging plate. The dichroscope may be used to determine the position of the vertical axis and accordingly of the base perpendicular to it. Benitoite crystal structure: Crystal structure of benitoite, BaTiSi3O9, P-6c2, projected onto the (a,c) plane. Because of its rarity, gemstones and mineral specimens of benitoite are extremely expensive. Sapphire has a Mohs hardness of 9, while benitoite is much softer at 6 to 6.5. The benitoite deposit is located in one of these basic inclusions, a portion of which has a somewhat schistose structure, while the rest is nearly massive. The eastern extension of such a shoot would have been removed by erosion and the western extension would be underground, to the north of, west of, and below, the open cut. Benitoite is insoluble in ordinary acids, but is attacked by hydrofluoric acid and dissolves in fused sodium carbonate. Benitoite was named California’s official state gem in 1985. In 1985 Benitoite was named the official state gem of California. Other rare gems and minerals include Neptunite, Joaquinite, djurleite, and Natrolite. According to Mr. Couch, specimens given to Harry U. Maxfield, of Fresno, were shown to G. Eacret, of Shreve & Co., San Francisco, and to G. D. Louderback. The incline shaft was apparently sunk in the lower part of this outcrop and did not encounter benitoite. Benitoite is a rare gemstone / mineral that fluoresces when lit by black lights. Fluorescent benitoite: This is a photograph of small benitoite crystals under ultraviolet light. Benitoite, a barium titanium silicate, can occur in rich blue crystals that are as striking and flawless as the finest sapphires. Material taken to Los Angeles by Mr. Hawkins was pronounced volcanic glass and valueless. Other forms are rather rare and of small importance. The brilliancy is due to the high refractive index and the fire or red flash, often seen in dull or artificial light is, in part at least, caused by the dispersion of the mineral. These facts point to the same period of formation for the three minerals with the power of crystallization arranged in the following order: neptunite, benitoite, and natrolite. The fractures and joints with the vein filling are about parallel with the schistosity of the rock, which averages nearly east and west in strike with local variations and has a varying dip of 20Â° to 70Â° N. A sketch map of a small area on the benitoite mine hill giving the outcrops with their dips and strikes and the formations encountered in the mine workings shows the schist and gabbro inclusion in the serpentine to be quite irregular in shape. Benitoite is a very rare and beautiful dark blue gemstone. This knob is called the apex, and from it a small spur extends to the west down to the creek. Streak: is white. The mineral exhibits a brilliant blue color under ultraviolet radiation. Hessel predicted the ditrigonal dipyramidal class of crystallization in 1830, and when minerals were found in San Benito County in 1907 with this crystal habit, his hypothesis was confirmed. A couple of other regions where the stone is found does not have gem-quality crystals of Benitoite… This ledge also carries a streak of natrolite with benitoite. Benitoite is an extremely rare mineral that is best known for being the official state gemstone of California. The principal production is in stones weighing less than 1 1/2 carats. The Benitoite Gem mine is located on a small mining claim (the Dallas claim) in San Benito County, California, about halfway between Los Angeles and San Francisco. Welcome to Benitoite.Com.. In some of the inclusions the gradation from the hornblende rock containing much natrolite to natrolite containing acicular inclusions of hornblende is complete. Benitoite fluoresces under short wave ultraviolet light, appearing bright blue to … This serpentine is of the usual
Typically, benitoite occurs in combination with minerals which make up the host rock. The color of benitoite is not affected by heating the stone to redness and allowing to cool. The strike encountered in the tunnel, about 30 feet lower and to the north, was nearly cast and west with a dip of about 40Â° N. In the upper part of the face of the open cut the dip was high, about 65Â° N., and below the middle of the face it was low, 15Â° to 25Â° N. Along the north side of the open cut and in the lower cut the strike was about east and west and the dip was probably rather low, 20Â° to 30Â° N. These measurements do not agree closely with those of Doctor Louderback, especially in regard to the dip of the vein. The richest colors are seen when the crystals are viewed parallel to the base. The writer observed benitoite in place through a distance of about 170 feet in an east and west direction. It often referred to as the “blue diamond,” a very rare gem that varies in its hue, from light transparent to dark blue, to saphire blue or sometimes violet shad, which was found first on San Benito River headwater in 1907 (which is why the name is named). Benitoite (be-NEE-toe-ite) is interesting and unique from a number of viewpoints. Development work at the benitoite mine at the time of the writer's visit consisted of a large and a small open cut, a prospect drift or tunnel with a crosscut tunnel, and an incline shaft. Benitoite from these three locations, all within a 10 km radius of the Benitoite Gem mine is generally very poor in quality but the classic triangular shaped crystals are found at each locality. Where can benitoite be found? It has a prismatic cleavage and the thin splinters or powder show a deep reddish-brown color. Benitoite is the state gemstone of California. This forms environments characteristic of subduction zones at convergent plate boundaries in low temperature, high pressure settings. Benitoiteâs identification and original description was based upon specimens found in the headwaters of the San Benito River, in San Benito County, California, from which it received its name. Forming in low temperature, high pressure environments, Benitoite is an extremely rare blue barium titanium cyclosilicate, found in hydrothermally altered serpentine. Benitoite crystals exhibiting two shades of color, as dark and light blue or blue and colorless in different parts of the same crystal, may be cut so as to show these variations, or sometimes in such, a way that the resulting color is of nearly uniform intensity. The color of one of the rays becomes stronger as the crystal is rotated from this position. Benitoite is also found, frequently, as gray to greenish colored crystals with very heavy inclusions of the amphibole crossite. The only significant locality for Benitoite is the Diablo Range, near the headwaters of the San Benito River, in the Southern tip of San Benito Co., California. About 30 feet S. 60Â° E. of the upper end of the huge open cut a ledge of altered blue hornblende schist outcrops prominently. At the top, you’ll find medium-dark stones. Doctor Louderback states that benitoite lias been found for a distance of about 230 feet at the surface along the mineral zone and in very small quantity at its extremes. A specimen was sent to the University of California, Berkeley in 1909 where mineralogist Dr. George D. Louderback discovered it was a mineral that was previously unknown. Gem quality stones and unbelievable mineral specimens can only be found one place on earth, a small 40 acre parcel of land in the Diablo Mountain Range of San Benito County California. Under long-wave UV light, the clearer to white benitoite crystals fluoresce green. It is a rare mineral found in very few areas, including California, San Benito County, Japan and Arkansas. Access to the mine is via either a roughly sealed trail that is privately controlled or by two alternate dirt roads that approach from the west and north of the gem mine. The meaning of the name of this stone relates to the location where they were first found, in a It is an extremely rare rock. These bowlders have evidently rolled from the outcrop on the hill above and probably from near the mine. The prospect tunnel was driven 120 feet in a direction N. 70Â° E. from the end of the large open cut. Typically color zoned, Benitoite comes in various shades of blue to white and, occasionally, colorless or pinkish. It is a barium titanium silicate mineral, typically of a blue color, found in hydrothermal rocks with a chemical composition of Ba Ti(Si 3O9). Benitoite mine map: Map showing the location in San Benito County in central California. Kay Robertson Collection Here is a beautiful crystal of the Zeolite Group species, Natrolite. The most widely used minerals are: natrolite, neptunite, joaquinite, serpentine and albite. Of the colors produced by dispersion during the refraction of light in benitoite yellow and green are largely absorbed in the colored gems so that principally red and violet-colored lights are seen. It is a mineral rarely seen in jewelry or gem and mineral collections. Gem-quality crystals have been found only in San Benito County, California. The size of the gems cut from benitoite range in weight from a small fraction of a carat to several carats. Photo by TheGemTrader.com. The hardness is greater than orthoclase and less than peridot, or about 6 to 6 1/2, and the specific gravity is 3.64 to 3.67. The end of the southward extension of this ridge is a low knob about 160 feet above the creek. By carefully cutting into these lumps beautiful crystals are sometimes uncovered. Benitoite is a rare blue silicate mineral, found in hydrothermally altered serpentinite. The schist near the vein is composed of bluish hornblende and actinolite needles penetrating granular masses of albite. In the latter places the benitoite projects into the cavities along with the coarse drusy surfaces of the natrolite. Fracture: is irregular. USA hand faceted, no treatments. Benitoite gemstones have a sapphire-blue color, and can have very good transparency and luster. Photo # 6 shows the Benitoite rough material that this was cut out of, Photo # 7 shows where the Benitoite was mined at and purchased from. In some specimens the following minerals are determinable under the microscope: augite, plagioclase crushed and recrystallized and containing clinozoisite prisms, secondary albite, yellow serpentine, and a little titanite and pyrite. The benitoite is obtained by breaking open masses of vein rock and carefully chiseling or working the crystals out of the inclosing natrolite. Photo by TheGemTrader.com. The benitoite is embedded in or attached to natrolite, being in some places completely, in other places partly, enveloped by it. It is a rare mineral found in very few areas, including California, San Benito County, Japan and Arkansas. These phases were probably originally different adjacent formations that have been metamorphosed. Pale-colored stones should be cut with the table perpendicular to the base or parallel to the vertical axis of the crystal to secure the full color value. The vein is a highly mineralized shattered zone in the schistose rock. A few more kilometers to the south and benitoite could have ended up with an entirely different name! The Benitoite Gem Mine filled one of the largest voids in the mineral world in spectacular fashion. Public domain image by Perditax. Underground this rock occurred in large loose spheroidal bowlders ranging up to several feet in thickness, with large openings between them. . ). Whether he discovered it while out alone or on a second trip with L. B. Hawkins, of Los Angeles, is a point in dispute. Clarity improves quality, particularly eye clean or better scores. It occurs in black to reddish- black prismatic crystals of the monoclinic system, the length commonly being several times the thickness. So far benitoite has been found at one place only. The mineral’s unique crystals are of great value as collectable samples. The birefringence is high and the pleochroism very strong.  The only location where gem-quality material has been found is in San Benito County, Califor… Small amounts of benitoite have also been found at other locations in California, Arkansas, Montana, Australia, Czech Republic, Japan, and Romania. It forms in low temperature, high pressure environments typical of subduction zones at convergent plate boundaries. Specimen and photo by Arkenstone / www.iRocks.com. Benitoite is a rare blue barium titanium cyclosilicate, found in hydro-thermally altered serpentinite. He named it benitoite for its occurrence near the headwaters of the San Benito River in San Benito County, California. This gem is almost always blue (it was originally thought to be a sapphire) but also has variations in purple, pink, and clear. The majority of larger cut stones weigh from 1 1/2 to 2 carats. It occurs only in the most mineralized region of California, the New Idria Mining District, in San Benito Country / USA (more than 150 semi-precious minerals and gemstones). The contact was evidently a fault line, and near it the serpentine contained much talcose and scaly asbestiform material. J.F.C. Dec 10, 2020 - Benitoite is the state gem of California. According to Doctor Louderback the largest perfect stone so far cut weighs over 7 carats and is about three times as heavy as the next largest flawless gem so far obtained. Their hair is cut short, parted to the side. 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