SCFM News March 02, Featuring Benitoite

 

 

MINUTES OF THE SO. CALIF. CHAPTER OF THE FRIENDS OF MINERALOGY

                    Desert Discovery Center, Barstow, CA---March 23, 2002

                                     Submitted by Al Wilkins, Secretary

Present:  Mary Aruta, Garth Bricker, Bob Housley, Bill & Pat Kent, Paul Malone, Walt Margerum, Gene Reynolds, Bob Reynolds, Jennifer Rohl, Al Wilkins

 

Treasurer’s Report:  Bob Housley reported that SCFM was solvent.  He indicated that he had submitted the necessary paperwork to apply for membership in CFMS, in order to secure, among other things, insurance to protect the club and its officers and agents while conducting club business.  Along with the application, Bob sent in $4.50 for each SCFM member as of 12/31/01.  The application is to be considered at the next CFMS Board meeting in April 2002.  Bob H. added that lots of copies of “Minerals of the Mojave” are still available.  Mary volunteered to try to sell them at the Desert Research Symposium on April 20.  Bob H. will attempt to drop them off with Mary or Bob R. before that time.

 

“Minerals of California” Photo Exhibit:  Bob Reynolds, Mary Aruta and Bob Hilburn, curator of the Desert Discovery Center (DDC) in Barstow, have collaborated to mount 33 photos on poster board and then hang them on the west wall of the DDC with Velcro fasteners.  Some of the photos were donated by Sugar White and by Anthony Kampf of the L.A. County Museum.  They cover 5 distinct themes---Mojave Sulfate Minerals (7); Wulfenite from the Blue Bell Mine (6), Pseudomorphs (6); Hexagonal Crystals (7); and California Gemstones (7).  Another 18 photos featuring “Minerals of Mexico” have been mounted on foam board and are on the table displays at the DDC.  We also have another collection of “Minerals of Africa,” runners-up from the Werner Lieber Photo Contest in Tucson, which have not yet been displayed.  Bob R. indicated that the Maturango Museum in Ridgecrest and the Shoshone Museum may be interested in similar photo displays, and that perhaps several of the local desert museums could rotate photo displays on various themes.  Jennifer is currently working on loading the photo images on the SCFM website.  Bob R. indicated that he would like museum curators to request certain minerals themes before he compiles photos to send them.

            It was proposed that each of us should bring our highest quality California thumbnails and small cabinet specimens to an upcoming meeting to be arranged at JMCC, so that they can be digitally photographed at that meeting and then returned home to their owners the same day.  Walt has a 2-megapixel digital camera which he will set up and experiment with.  He indicated a tif format would yield better image quality than jpg and that the largest photo that could be produced from a digital image in either case would likely be 8” x 10”, which all those present seemed to think was acceptable.  Gene offered to bring in his double-tube fiber-optic light source for this purpose.

 

Next SCFM meetings:  The date and site of the next SCFM meeting is still pending.  Al will call Garth next week to find out what he has heard from Cal Graeber regarding his availability for a future meeting at the Fallbrook Museum.  Bob R. will talk to Mary Burns at the JMCC regarding the availability of that site as well.  Gene reported that the JMCC classroom is now heated, air-conditioned, and carpeted.  Bob R. recommended investigating the U.S. Borax Visitor Center or the 20 Mule Team Museum in Boron as possible SCFM meeting sites for the future.  Temecula also has potential.  He also reported that the new convention center at Ryan is eager to host the SCFM meeting in October, perhaps to focus on borates.  He advised up to think about who we would like to hear speak, especially given the recent passing of our friend Jim Minette; the name of Bill Smitheram, whose father had previously worked at Ryan, was raised.  Bob R. indicated that he had not as yet broached the topic of a field trip in conjunction with the Ryan meeting.  There is a need to update our collection of borate photos before the Ryan meeting.                                                                                                                                 

 

Upcoming Events:              SCMM meeting – June 15, 2002 @ JMCC

            NCMA Micromount Conference June 22-23, 2002 @ Pollock Pines, CA

 

Web site address:   http://www.mineralsocal.org, then click on Southern California Friends of Mineralogy in the upper right hand corner.  If you have new locality information, please access that section of the site to complete a locality form.

 

Secretary’s Note:  As the newly appointed Secretary of SCFM, I would like to offer the alternative of e-mail transmission of the SCFM meeting minutes/newsletter, for your convenience and to save the group mailing costs.  If interested, please send your e-mail address to:  alan.j.wilkins@kp.org.  If I don’t hear from you, you will continue to receive SCFM mailings at your snail mail address.  I would also like to begin a new feature spotlighting minerals with California type localities.  This issue, I will feature benitoite, the California state gemstone.  I would also like to encourage all SCFM members to relay any item(s) of general interest to me for inclusion in future newsletters.  In addition to my e-mail address above, I can be reached by FAX at (949) 589-8608 or at:  23202 Via Celeste, Coto de Caza, CA 92679-3919.

 

Current SCFM Officers:  President – Bob Reynolds; Vice-President – Garth Bricker;

            Treasurer – Bob Housley; Secretary – Al Wilkins

SCFM Board:  Bob Reynolds; Jack Nieburger; Dan McHugh; Kay Robertson; Bob Varish

 

National FM Board of Directors:  Bob Reynolds; Jack Nieburger

 

 

SCFM Mission Statement:  Members of the Southern California Chapter of the Friends of Mineralogy (SCFM) are collectors, museum curators, amateur and professional mineralogists, and educators devoted to propagating interest in mineralogy.  For all our diverse backgrounds, we are united in our desire to see minerals appreciated and understood.  Our goals are to bring about a coalescence of professional and amateur mineralogists, to offer the Chapter’s services and resources to Southern California natural history museums, and with them to establish definitive, comprehensive collections of California minerals.  SCFM is a non-profit organization that meets 6 times each year, at a variety of mineralogically interesting institutions in Southern California, and hosts an annual symposium on topics of interest to professional and amateur mineralogists alike.  Museum workshops in March and October supplement general meetings.  Annual membership dues of $10 include membership in the national organization, Friends of Mineralogy. 

            SCFM is not responsible and cannot be held responsible or liable for any person’s injuries, damages or loss of property at or traveling to or from any general meetings, board meetings, workshops, field trips, or any other SCFM event.

 

2002 SCFM Dues:  If a red dot appears to the left of the address label on this newsletter, then your 2002 SCFM dues are outstanding.  In that case, please send your check for $10 per member to SCFM Treasurer Bob Housley @ 255 S. Wilson Ave. #2, Pasadena, CA 91106.

 

 

                                   BENITOITE - THE CALIFORNIA STATE GEMSTONE

 

by Al Wilkins

 

Classification:  Cyclosilicate.

 

Formula:  BaTiSi3O9.

 

            Crystallography:  Hexagonal (P6c2).  Trigonal and hexagonal plates and platelets: {0001}, {0111), {1011}, {1010}, {1012}, {10.1.9.10}.  Crystals are triangular, flattened on the c axis, and pyramidal or tabular.

 

Color:  Blue (various shades), also colorless and white; rarely pink to purplish blue. 

 

Luster:  Vitreous.

 

Streak:  White.

 

Hardness:  6-6.5.

 

Specific gravity:  3.65-3.70.

 

Cleavage:  {1011}, imperfect.

 

Fracture:  Conchoidal to uneven, brittle.

 

Toughness:  Fair; brittle.

 

Refractive indices:  o = 1.756-1.759; e = 1.802-1.804.  Uniaxial (+).

 

Pleochroism:  Strong: o = colorless; e = blue.

 

Clarity:  Translucent to transparent.

 

Birefringence:  0.043-0.047.

 

Dispersion:  0.046.

 

Fluorescence:  Intense bluish white under SW (254 nm).  Occ. dull red under LW (365 nm).

 

Cathodo-luminescense:  Intense blue.

 

Stability:  Sensitive to rapid temperature changes and ultrasonic vibration.

 

Solubility:  Insoluble in hydrochloric and sulfuric acids, but readily attacked by hydrofluoric acid.

 

Faceting information:  Critical angle - 34.7o; Optimum crown angle - 38o; Optimum pavilion angle - 41o.

 

Type locality:  Benitoite Gem mine (previously the “Dallas Gem mine”), San Benito Co., CA.

 

            In 1907, J.M. Couch of Coalinga, grubstaked by R.W. Dallas, was camping in a wooded

glade in the Diablo Range above the mercury-mining town of New Idria.  Waiting in his bedroll for the morning chill to subside, he was surprised to see the sun reflected by “thousands of blue gems” on the slope above his camp.  Specimens were delivered to lapidary Harry U. Maxfield of Fresno, who declared the stone spinel, finding it too soft to be sapphire.  He showed some of the stones to George Eacret of Shreve & Co., one of the largest jewelry stores in San Francisco at the time, who believed they were sapphires.  Eacret used a dichroscope to determine that the stone was doubly refractive and delivered a sample to Professor George D. Louderback of the University of California (Berkeley).  Louderback analyzed the material, made extensive crystal drawings, and paid close attention to the etch figures on each of the faces.  The p and ii faces were found to be symmetrically unrelated, proving the existence of a 6-fold axis.  He eventually concluded that the material represented a new mineral, which he named benitoite after the county of its discovery and the river which had its headwaters nearby.  The subsequent atomic arrangement of benitoite determined by Zachariasen (1930) confirmed Louderback’s conclusions.  Louderback described the three major minerals of the Benitoite Gem Mine area—benitoite, neptunite, and joaquinite---in his classic paper in 1909.

            Benitoite became an immediate sensation after Louderback’s description in 1909, partly because of its beauty and partly because it was the first mineral in the previously theoretical crystal class 6m2 (P6c2)—the ditrigonal-dipyramidal class of the hexagonal crystal system, predicted mathematically by Hessel some 77 years prior to its discovery.  Unlike the common cyclosilicates beryl, cordierite, and tourmaline, whose structures are based upon circular rings of six SiO4 tetrahedra, benitoite is based upon three tetrahedra linked together to form a triangular group.  Two other equally rare minerals have now been identified as sharing this structure with benitoite:  bazirite [BaZrSi3O9], found most prominently on Rockall Island, Inverness-shire, Scotland; and pabstite [Ba(Sn,Ti)Si3O9], found only in the Kalkar limestone quarry in Santa Cruz Co., CA, now the site of a housing development.

            After the discovery of benitoite, the Dallas Mining Company built cabins and corrals nearby, and mining equipment was hauled in by horse and wagons over tortuous roads from Coalinga.  Active mining began in July 1907.  Dallas patented two claims of 20 acres each and mined the veins for benitoite gem material between 1907 and 1912, when it ceased to be economical.  The mine was not issued patent papers until 1917.  Dallas initially liberated benitoite from the natrolite veins with chisels and a punch press; many crystals were broken this way.  HCl dissolution of natrolite was later showed to be effective, but was judged to be too time-intensive, and the earlier, more primitive extraction methods were again resorted to.  After 1912, little further mining was done until the mine was leased by Miller Hotchkiss of Firebaugh, CA in the 1940s, and a bulldozer was utilized for the first time to work the mine tailings.  From 1952 to 1967, Clarence Cole, a mineral dealer from Oakland, held the lease and used a bulldozer and dynamite to enlarge the pit.  In 1966, Cole granted a sublease to Gerold Bosley of San Diego, backed by the noted mineral dealer Josephine Scripps.  Cole died in 1967, and the lease was subsequently transferred to William C. “Bill” Forrest of Fresno, CA and  Elvis L. “Buzz” Gray, currently of Missoula, MT.  Forrest and Gray purchased the mine from the Dallas family in 1987 and remain the sole owners today.  Most of the best specimens of neptunite, benitoite, and jonesite have been produced by Forrest and Gray, who initially hand-picked mineralized blueschist and loose pieces of benitoite from the dump, then took great care in removing the natrolite from the crystals they found.  Since 1982, the owners have used a more mechanized recovery process utilizing a front-loader feeding dirt and rock through a grizzly into a hopper, where material is successively washed and screened, with visual inspection and hand-picking of rough gem benitoite at the end of each work day.  By the end of 1996, the colluvium and eluvium at  the Benitoite Gem mine area had been nearly completely worked out, but a new productive area to the west, downslope from the historic pit, was identified in the spring of 1997.  Still, only limited production of benitoite gemstones is anticipated in the future.

            It is estimated that a total of 2,500 carats of faceted benitoite was produced from 1907 until 1967, when Forrest and Gray began working the mine; of that, 1,000 carats were produced in the first four years of the mine’s existence.  Since 1967, Forrest and Gray have produced about 2,000 carats of faceted benitoite.  An estimated 500 carats of faceted benitoite have entered the market from other sources, such as the cutting of old rough and the faceting of mineral specimens.  Thus, a total of 5,000 carats of faceted benitoite was produced by the Benitoite Gem Mine as of 1997.  Good quality gems cut from benitoite are seldom larger than one carat, since crystals are typically badly flawed and since the best color (along the e axis) is seen in the disadvantageous direction in terms of flattening the crystals.  Of the faceted stones produced by Forrest and Gray, 89% of them have been under 1 carat; 9% ranged from 1 to 2 carats; and 2% have been over 2 carats; benitoite gemstones over 3 carats are exceedingly rare.  

            The benitoite mine, popularly called the “Dallas mine” until the mid-1960s and subsequently as the “Dallas Gem mine,” has been designated as the “Benitoite Gem mine” by its current owners, after the notation on U.S. Geological Survey topographic maps of the site as the “Gem mine.”  The mine is located on the southern end of the Diablo Range, in the western San Joaquin Valley of California, 20 miles northwest of the town of Coalinga, in the New Idria district.  The New Idria district was established in 1853 with the discovery of a rich mercury deposit, but it is also known for its chromium, asbestos (short-fiber chrysotile), gold, and gemstone resources.  The Benitoite Gem mine’s elevation is approximately 4,520 feet.  It is located on 40 acres of private, patented mining property, secured by a locked gate, and patrolled regularly by law enforcement officers.  Access from either the southwest or the northeast requires about 20 miles of driving over a network of rough 4-wheel-drive trails maintained infrequently by the U.S. Bureau of Land Management.  Geologic maps of the mine were first prepared by Coleman (1957), and later by Rohtert (1994) and Laurs (1995).  Laurs, Rohtert and Gray (1997) did extensive geologic mapping and collected chemical data on blueschist minerals and whole-rock samples at all known benitoite occurrences in the New Idria district.  Based on those studies, they have hypothesized that benitoite formed at the Bentoite Gem mine when Ba and Ti were released by the alteration of blueschist, and possibly greenstone, in the presence of magnesium- and calcium-rich fluids generated during the regional metamorphism of serpentinite.

            The Diablo Range is composed of rocks of the Jurassic Franciscan formation (graywacke, shale, chert, and basalt), intimately associated with serpentinite in the New Idria area.  In the Franciscan block containing the Benitoite Gem mine, graywacke has been metamorphosed to greenstone and basalt to blueschist, subsequently altered to felted masses of actinolite or crossite fibers.  Solutions periodically percolating through fracture systems there have formed veins consisting primarily of albite, crossite, and epidote.  The mineralized zone is at least 60 meters long, strikes N60oW, dips moderately northeast, and is about 3 meters thick.  Benitoite crystals attached to the walls of cross-cutting veins are generally well formed and of an exceptional blue color, while those filling pore spaces in altered blueschist typically have a dull, frosted, porous appearance, deriving from abundant inclusions.  Common benitoite inclusions are the amphiboles actinolite-tremolite and crossite; the pyroxenes aegirine-augite and diopside; silica pseudomorphs after serandite; reddish-brown neptunite; and honey-colored joaquinite-group minerals.  Other reported inclusions include albite, apatite, and greenish-gray djurleite.  Rarely, non-gem benitoite crystals form star-shaped penetration twins via a Dauphine-type 180o rotation about the c axis; only nine twinned crystals have been recovered thus far by the current mine owners.

            Tentative age data suggests that the benitoite crystallized about 12 million years ago, making it much younger than the enclosing blueschist, which formed between 100 to 160 million years ago.  Minerals formed at about the same time as benitoite include albite, apatite, jonesite, and the copper sulfides djurleite, digenite, and covellite.  Later, natrolite coated the earlier-formed minerals and filled most of the remaining pore spaces.  Other associated minerals include: neptunite, joaquinite, fresnoite, banalsite, silica pseudomorphs after serandite, calcite, and aragonite.

            Four other benitoite prospects in the New Idria district include: (1) the Junnila claim, first worked in 1982, producing translucent, tabular crystals in blue, colorless, or color-zoned varieties, averaging 1 cm in their maximum dimension, though a few crystals of up to 2.6 cm have been suitable for faceting; (2) the Numero Uno claim, producing pale blue, platy, euhedral crystals up to 5 mm in diameter; pale blue to colorless tabular, pseudo-hexagonal plates and rosettes up to 10 mm in diameter; and, less commonly, tan grains, described as “pink” by Chromy (1969); (3) the Victor claim, first staked in 1974, producing colorless benitoite platelets and rosettes up to 5 mm in diameter; and (4) the Santa Rita Peak property, controlled by the Kennecott Exploration Company, on which electron microprobe analysis has revealed microscopic crystals of benitoite in altered blueschist.  All of the aforementioned localities are closed to public collecting.  Of these, only the Benitoite Gem mine and the Junnila mine have produced gem-quality benitoite material, and only the former has yielded commercial gem production.

            Outside the New Idria district, benitoite has been found in situ at only four other areas.  At the Big Creek-Rush Creek confluence, in eastern Fresno County, small grains of stannian benitoite, containing up to 4.1 wt. % SnO2, are found in gneissic metamorphic rocks near granodiorite, first reported in 1965.  In Japan, benitoite was reported in 1973 from albite-amphibole rock in a serpentine body along the Kinzan-dani River, at Ohmi in the Niigata Prefecture, containing 1.77 wt. % ZrO2.  At Broken Hill, New South Wales, Australia, benitoite was reported in high-grade granite gneiss in 1982.  More recently, 1-2 mm crystals of colorless, blue, and pink benitoite were detected in gas cavities in syenite at the Diamond Jo quarry in Hot Springs Co., Arkansas.  Two previously reported benitoite locations, Esneux and Streupas in the Owithe Valley, Belgium (1928) and sands of the Eocene Cook Mountain formation of southwest Texas (1931), have subsequently been discredited.

            The measured amounts of Ba, Ti, and Si in benitoite are remarkably constant (BaO 37.09%, SiO2 43.59%, TiO2 19.32%), regardless of color or locality, and fall near the ideal values that are calculated from the chemical formula.  The appearance of benitoite crystals is quite variable, however.  A few are gemmy and deep to pale blue.  The vast majority, however, are translucent with whitish centers and blue outer rims.  Detailed electron probe analysis by Laird and Albee (1972) indicated that the composition of the white and blue parts of the crystal were identical.  Those crystal faces having a stoney appearance are pale blue-gray because of abundant crossite inclusions, and most of them contain prominent etch pits.  Average benitoite crystal sizes are 1 to 1.5 cm, and crystals greater than 2.5 cm in diameter are considered large.  Wise & Gill (1977) describe a well-formed crystal measuring 5.6 cm in the collection of the Geology Department of Pomona College in California.  A fine matrix specimen obtained by Josephine Scripps in 1956, measures 21.6 x 12.7 cm (8.5" x 5") and is pictured in The World’s Finest Minerals and Crystals by Dr. Peter Bancroft.

            Benitoite is considered one of the most beautiful of all the rare gems and, lacking cleavage, is one of the easiest to facet.  Its color varies from a very pale blue to a deep purplish blue; the color of the finest benitoite (often referred to as “cornflower blue”) rivals that of fine sapphire.  Its dispersion approaches that of diamond and is best shown when faceted as a round brilliant or as a trilliant.  Color zoning is occasionally seen, especially in emerald-cut stones, which can display a characteristic blue-to-colorless pleochroism when viewed face-up with the unaided eye.  The violaceous tints are attributable to its strong dispersion (similar to that of diamond), often apparent as the stone is turned.  Colorless gems are uncommon.  Rare specimens have a strong reddish component and exhibit pink-to-blue dichroism.  Heat treatment of lighter-colored material may result in an orange hue similar to that associated with Imperial topaz; the orange color has not been observed in untreated benitoite.  Spectrophotometry of blue benitoite reveals a broad peak at about 700 nm, most of which appears in the near-infrared region.  In spite of much study of spectral data and the chemical composition of benitoite specimens, a chromophore has not been identified; attributions of its blue color to reduced Ti; trace impurities of V, Nb and Cu; crystal defects due to oxygen deficiency; metal-metal charge transfer; traces of Zr at the Ti site; and traces of Fe3+ have not been substantiated in the laboratory. 

            Distinguishing benitoite from other blue gemstones is generally not difficult for a gemologist.  Its high birefringence, strong dispersion, and its blue-to-colorless pleochroism distinguishes it from sapphire.  Natural and irradiated blue diamonds can have the appearance of lighter shades of benitoite, but can be easily distinguished from benitoite by being singly refractive and possessing a much higher refractive index.  Benitoite may be distinguished from tanzanite by its lack of the purple trichroic component almost always present at some angle in tanzanite.  Sapphirine is generally too dark to be confused with benitoite, and zircon does not possess the same hue.  Cordierite (iolite) and blue tourmaline (indicolite) show much lower dispersion, refractive indices, and birefringence than benitoite.  In addition, benitoite commonly has distinctive growth-zoning and the lint-like mineral inclusions described above.

            The largest known faceted benitoite gemstone weighs 15.42 carats and was cut from rough recovered in the early 1990s; another exceptional gem weighs 10.47 carats and was cut in the late 1980s.  A third benitoite gemstone worthy of mention weighs 7.53 carats (after being re-cut) and is part of the National Gem Collection housed at the Smithsonian Institution in Washington, D.C.  Gray and Forrest made a set of benitoite jewelry, consisting of a ring, earrings, and a diamond necklace with a pendant centered with a flawless 6.53 carat pear-shaped brilliant benitoite in 1974.  The set was shipped to Zurich, Switzerland, where it was stolen from the airport.  All but the pendant was recovered within a year of the theft.

            Synthetic benitoite has been successfully grown in the laboratory, but only in minute, colorless crystals that are too small to facet.  Natural benitoite has an important industrial application in electron microprobes, being used to align and adjust the beam size.  Benitoite is also employed as an analytical standard for Ba and Ti, because of the consistency of its chemical composition.    

            The ultraviolet response of benitoite is interesting.  Under SW (254 nm), benitoite fluoresces an intense blue-white, the paler-colored cores frequently more vividly than the edges.  Under LW (365 nm), the cores fluoresce a dull red, while the edges are non-fluorescent.  Both SW and LW responses are more pronounced in colorless and lighter-colored benitoite specimens.

            California State Bill AB-2404, proposed by Lucy Killea of the 78th District and Rusty Areias of the 25th District, officially designated benitoite as the California State Gemstone in 1984, taking its place with native gold, the California State Mineral (designated 1965), and serpentine, the California State Rock (also designated 1965). 

            The emblem of the California Federation of Mineralogical Societies is a triangular form surrounding the famous Golden Bear Nugget (pictured on the Centennial Volume of Minerals of California—Bulletin 189).  The points of the triangle are truncated to represent the crystal form of benitoite.

           

CHRONOLOGICAL BIBLIOGRAPHY:

 

Hessel J.F.C. (1830) Krystallometrie.  Reprinted as:  Nr. 88.  Ostwald’s Klassiker der exakten                            Wissenschaften (1897), Wilhelm Engelmann, Leipzig.

                        Louderback G.D. (1907) Benitoite, a new California gem mineral (with chemical analysis by W.C. Blasdale).  University of California, Department of Geological Sciences Bulletin 5, pp. 149-153.         

Arnold R. (1908) Notes on the occurrence of the recently described gem benitoite.  Science 27, No. 686, pp. 312-314.

Rogers A. F. (1908) Notes on the crystal form of benitoite.  Science 28, p. 616.

Louderback G.D. (1909) Benitoite, its paragenesis and mode of occurrence.  University of California, Department of Geological Sciences Bulletin 5, pp. 331-380.

Palache C. (1909) Note on the crystal form of benitoite.  American Journal of  Science 27, p. 398.  

Sterrett D. B. (1911) Benitoite.  U.S. Bureau of Mines and Minerals 1909 Yearbook, Part. 2: Non-metals.  Washington, D.C., pp. 742-748.

Bradley W.W., Huguenin E., Logan C.A., and Waring C.A. (1917) Mines and Mineral Resources of the Counties of Monterey, San Benito, San Luis Obispo, Santa Barbara, Ventura.  California State Mining Bureau, San Francisco, pp. 42-43.

Anten J. (1928) Sur la composition lithologiques des psammites du Condroz.  Societe Geologique de Belgique, Annales 51, pp. B330-331.

Zachariasen W. H. (1930) The crystal structure of benitoite, BaTiSi3O9.  Zeist. Kristallogr. 74, pp. 139-146.

Lonsdale J.T., Metz M.S., and Halbouty M.T. (1931) The petrographic characters of some Eocene sands from southwest Texas.  Journal of Sedimentary Petrology 1, pp. 73-81.

Payne C.J. (1939) Dispersions of some rarer gemstones.  Gemmologist 9, pp. 33-35. 

Pabst A. (1951) Minerals of the serpentine area in San Benito County, California.  Rocks and Minerals 26, pp. 478-485.

Rase D.E., and Roy R. (1955) On the stability and hydrothermal synthesis of benitoite.  American Mineralogist 40, pp. 542-544.

Coleman R.G. (1957) Mineralogy and petrology of the New Idria district, California.  Ph.D. dissertation, Stanford University, Stanford, CA.  (See Dissertation Abstracts 17, No. 17, p. 1533).

Couch O. (1961) The Benitoite Story.  Independently published, 10 pp.

Lee D.E., Thomas H.H., Marvin R.F., and Coleman R.G. (1964) Isotopic ages of glaucophane schists from the area of Cazadero, California.  U.S. Geological Survey Professional Paper 475, pp. D105-D107.

Alfors J.T., Stinson M.C., Mathews R.A., and Pabst A. (1965) Seven new barium minerals from eastern Fresno County, California.  American Mineralogist 50, pp. 314-340.

Gross E.B., Wainwright J.E.N., and Evans B.E. (1965) Pabstite, the tin analogue of benitoite.    American Mineralogist 50, pp. 1164-1169.

Moller W.P. (1965) Minerals of southern San Benito County, California.  Gems and Minerals 331, pp. 28-32.

Chromy B. (1969) Pink benitoite.  Gems and Minerals, No. 279, p. 32.

Laird J. and Albee, A.L. (1972) Chemical composition and physical, optical, and structural properties of benitoite, neptunite, and joaquinite.  American Mineralogist 57, pp. 85-102.

                        Chihara K., Komatsu M., Mizota T. (1973) A new strontium-titanium hydrous silicate mineral from Ohmi, Niigata Prefecture, central Japan.  Mineralogical Record 7, No. 3, pp. 198-301.        

Bancroft P. (1976) La Benitoite, Californie, U.S.A.  Le Monde et Les Mineraux 11, pp. 258-261.

Sinkankas J. (1976) Benitoite (in) Gemstones of North America, Vol. II, Van Nostrand Reinhold, Princeton, NJ, pp. 280-288.

Wise W.S. and Gill R.H. (1977) Minerals of the Benitoite Gem Mine.  Mineralogical Record 8,

            pp. 442-452.   

Dibblee T.W., Jr. (1979) Geologic map of the central Diablo Range between Hollister and New Idria, San Benito, Merced and Fresno Counties, California.  U.S. Geological Survey Open File Map 79-358, scale 1:125,000.

Christophe M, Gouet G., Wyart J. (1980) Synthese hydrothermale de la benitoite.  Bulletin de

            Mineralogie 103, pp. 118-119.

Mitchell R.K. (1980) The fluorescence of benitoite.  Journal of Gemmology 17, No. 3, p. 149.

Millage A.H. (1981) Mineralogy of the Victor claim, New Idria district, San Benito County, California.  M.S. thesis, Stanford University, Stanford, CA.

Worner H.K. and Mitchell R.W., eds. (1982) Minerals of Broken Hill.  Australian Mining & Smelting Ltd., Melbourne, pp. 54, 87, and 202.

Bancroft P. (1984) Gems and Crystal Treasures.  Western Enterprises, Fallbrook, CA, pp. 94-95.

Gray M. (1986) Benitoite mining today.  Canadian Gemmologist 7, No. 3, pp. 82-83.

Hawthorne F.C. (1987) The crystal chemistry of the benitoite group minerals and structural relations in (Si3O9) ring structures.  Neues Jahrbuch fur Mineralogie, Monatshefte 1, pp. 16-30.

Austin D.H. (1988) The Benitoite Story.  Independently published, 80 pp.

Gubelin E.J. and Koivula J.I. (1988) Photoatlas of Inclusions in Gemstones, ABC Edition, Zurich, Switzerland.

Frazier S. and Frazier A. (1990a) A rare bit of history.  Lapidary Journal 44, No. 8, pp. 46-58.

Frazier S. and Frazier A. (1990b) A benitoite bibliography.  Lapidary Journal 44, No. 8, pp. 61-68.

Gray M. (1992) Recent developments at the Benitoite mine.  Canadian Gemmologist 13, No. 4, pp. 118-119.

Rohtert W.R. (1994) Preliminary geologic map of the Benitoite Gem mine.  Report submitted to the Kennecott Exploration Company, Reno, NV.

Barwood H. (1995) Benitoite and joaquinite in Arkansas.  Mineral News 11, No. 5, pp. 2, 5.

Laurs B.M. (1995) Progress report: Benitoite exploration in the New Idria mining district, San Benito County, California.  Report submitted to the Kennecott Exploration Company, Reno, NV.

Smith A.E. (1995) The reported benitoite occurrence in Texas—doubtful?  Mineral News 11, No. 5, p. 5.

Petrov A. (1995) More benitoite locality information, another new one and another discredited.             Mineral News 11, No. 8, p. 9.

Van Baalen M.R. (1995) The New Idria serpentinite.  Ph.D. dissertation, Harvard University, Cambridge, MA.

Wise W.S. and Moller W.P. (1995) Geology and mineralogy of the New Idria district, San Benito and Fresno Counties, California.  Rocks and Minerals 70, No. 1, pp. 27-35.

Moller W.P. (1996) A new discovery of benitoite.  Mineralogical Society of Southern California Bulletin, September, pp. 3-4.

Ream L.R. (1996) Benitoite from the Junnila mine.  Mineral News 12, No. 3, p. 3.

Laurs B.M., Rohtert W.R., and Gray M. (1997) Benitoite from the New Idria district, San Benito County, California.  Gems & Gemology 33, No. 3,  pp. 166-187.

Rossman G.R. (1997) Benitoite visible spectra (350-1100 nm).  Web page,