THE
MINERAL HERDERITE
- Chemistry: CaBePO4(F, OH), Calcium Beryllium Phosphate Fluoride Hydroxide.
- Class: Phosphates
- Uses: As a very minor ore of beryllium and phosphorus and as mineral specimens.
Specimens
Herderite is an attractive and except in some mines in New England, a rather scarce phosphate mineral. It forms good crystals and can have a nice yellow or light blue color. Its twinned crystals are its most note-worthy form although its simple prismatic crystals can have quite complex and interesting terminations. The twinning can produce some very non-monoclinic looking crystals that could easily confuse identification. Orthorhombic and nearly hexagonal twins are possible. A "fishtail" twin has also been seen from deposits in Brazil. To top-off this mineral, some specimens are fluorescent. A deep blue color can sometimes be seen under longwave ultraviolet light. Herderite, with its beryllium chemistry, possible fluorescence and both attractive and interesting crystal forms, is certainly a nice addition to anybody's collection.
PHYSICAL CHARACTERISTICS:
- Color is colorless, white, yellowish or pale green to blue-green.
- Luster is vitreous.
- Transparency: Specimens are transparent to translucent.
- Crystal System is monoclinic; 2/m
- Crystal Habits include prismatic crystals with a complex, but over all domal termination. The prism faces may be rounded and etched. Twinning is common forming cyclic twins that have a malformed hexagonal tabular crystal. The "malformation" usually results in a crystal that looks more orthorhombic than hexagonal and are easily confused with crystals of barite. Other types of twinning can form "fishtail" twins similar to gypsum's famous twins. Also found in nodules, fibrous aggregates, radiating clusters and small grains.
- Cleavage is indistinct in two directions (prismatic).
- Fracture is subconchoidal.
- Hardness is variable from 5 - 5.5
- Specific Gravity is approximately 2.9 - 3.0 (average)
- Streak is white.
- Other Characteristics: Thermoluminescent, meaning it may glow with a weak blue light upon extreme heating (but this test may damage the specimen). Also sometimes fluorescent, showing deep blue in longwave ultraviolet light.
- Associated Minerals include those minerals common to phosphatic grantite pegamtites.
- Notable Occurrences include Golconda Mine, Minas Gerais, Brazil; several locations in Germany and Mursinsk, Russia. It the United States there are several locations that produce plentiful supplies of good crystals such as Newry, Stoneham and Topsham, Maine; Fletcher Mine, Alexandria, New Hampshire and San Diego County, California.
- Best Field Indicators are crystal habit, color, fluorescence if seen, hardness and localities.
 Amethyst Galleries' Mineral Gallery MINERALS |
HERDERITE specimen her-1
$ 27.00
$ 27.00
Dims: 1.6 x 1.0 x 0.4" (4.1 x 2.5 x 1.0 cm)
Wt: 14.0 g
Corrego Frio, Divino da Laranjeiras, Minas Gerais, Brazil
This small thumbnail specimen consists of approximately 8 oddly-shaped Herderite crystals. These crystals range in length from 0.1 - 1.6" (0.3 - 4.1 cm) and are in excellent condition, as only one or two of the tiniest crystals are damaged or broken. The two largest crystals make up the bulk of the piece, and appear to make up a single twinned crystal, though their twinning is rather asymmetrical. Their monoclinic prismatic forms are very good, nonetheless, and their edges are very well-defined and their faces are heavily-striated but clean. A few of the faces possess a dull, almost waxy luster, but others have a much brighter, vitreous shine. Portions of the specimen appear to be heavily rust stained on the surface, but the Herderite essentially has a pale brown coloration. It is only dimly translucent, too. There is no host rock present.
her-1 ($ 27.00)
Corrego Frio, Divino da Laranjeiras, Minas Gerais, Brazil
HERDERITE specimen her-2$ 120.00
Dims: 2.7 x 2.3 x 1.7" (6.9 x 5.8 x 4.3 cm)
Wt: 3.05 oz. (86.7 g)
Linopolis, Divino das Laranjeiras, Minas Gerais, Brazil
Two intergrown Herderite crystals rest on the albite base of this hand specimen. The less-exposed of these crystals has dimensions of 1.1 x 0.9 x 0.4" (2.8 x 2.3 x 1.0 cm), whereas the smaller and more exposed crystal measures 0.8 x 0.5 x 0.4" (2.0 x 1.3 x 1.0 cm). Both are in excellent condition, showing almost no human-induced damage, and have complex but good monoclinic form- their edges are well-defined and their faces are striated but clean, possessing a pearly luster. Both have a pale yellow-brown coloration and are transparent but heavily internally-fractured; thus, they appear to be essentially translucent. The albite on which they rest consists of several intergrown crystals, many of which have a flat, almost tabular form. Upon exa
her-2 ($120.00)Linopolis, Divino das Laranjeiras, Minas Gerais, Brazil
HERDERITE specimen her-3
$ 125.00
$ 125.00
Dims: 1.5 x 1.1 x 0.7" (3.8 x 2.8 x 1.8 cm)
Wt: 18.8 g
Linopolis, Divino da Laranjeiras, Minas Gerais, Brazil
At least 2 Herderite crystals are intergrown to form this thumbnail specimen. One of the crystals is much smaller than the other two and is almost completely intergrown, so I will concentrate on the other two. They are of a similar size, measuring approximately 0.8 x 0.8 x 0.6" (2.0 x 2.0 x 1.5 cm), and are in very good condition, showing only slight damage along one edge of one crystal. Both show very good monoclinic prismatic form, though they are rather warped due to intergrowth with each other and with surrounding quartz crystals, most of which have been removed. Both crystals still have well-defined edges and clean faces that possess either a pearly or a waxy luster. They have a pale brown coloration and are dimly to moderately translucent due to intense internal fracturing. Some small areas, though, show evidence of dim transparence. A single, small, double-terminated quartz crystal is partly embedded in one of the Herderites, but there is no host material present.
her-3 ($125.00)
Linopolis, Divino da Laranjeiras, Minas Gerais, Brazil
HERDERITE specimen her-4
$ 60.00
$ 60.00
Dims: 2.0 x 1.0 x 0.9" (5.1 x 2.5 x 2.3 cm)
Wt: 21.6 g
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
A single, small Herderite crystal rests on the albite host rock of this specimen. It is rather short and stubby, measuring only 0.4 x 0.2 x 0.1" (1.0 x 0.5 x 0.3 cm), but is in excellent condition- the only damage done to the crystal is where it was broken off at its base, and a small chip at its termination tip. Its monoclinic prismatic form is very good, showing well-defined edges and generally clean faces that possess a bright pearly luster. Its color is a pale-dull green with a hint of creamy-brown and it is transparent and moderately clear, as internal fractures are visible. It rests horizontally on a flat, likely crystalline face of the albite that is coated with tiny nodular muscovite books or formations.
her-4 ($ 60.00)
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
HERDERITE specimen her-5
$ 34.00
$ 34.00
Dims: 1.0 x 0.8 x 0.6" (2.5 x 2.0 x 1.5 cm)
Wt: 7.9 g
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
I count at least 5 discernable Herderite crystals on the pale, dull pink base of this specimen. However, only 2 of these crystals exceed 2 mm in length, so I will concentrate on them. Both are in excellent condition, showing no damage whatsoever; the larger crystal measures 0.4" (9 mm) and the smaller measures 0.2" (6 mm) in length. Their monoclinic prismatic form is likewise excellent, with sharp edges and relatively clean faces whose luster ranges from waxy to pearly. Their color is a pale green, and both are transparent and impressively clear. They rest on a base of what appears to be several intergrown pseudohexagonal muscovite "books" that have been covered with a pale, dull pink crust of muscovite that has an unusual pattern. Pieces of a broken quartz and a broken schorl crystal are also partly embedded in the host.
her-5 ($ 34.00)
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
HERDERITE specimen her-6
$ 45.00
$ 45.00
Dims: 2.2 x 1.9 x 0.5" (5.6 x 4.8 x 1.3 cm)
Wt: 26.3 g
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
This large thumbnail specimen consists of an albite crust on which rest at least 13 Herderite crystals. Two of these crystals are visibly damaged and one is broken, but the others appear to be in excellent condition. They reach lengths of 0.6" (1.5 cm) and have good monoclinic prismatic form, with well-defined edges and clean faces. All have a pale greenish-gray color and a bright pearly luster, and are transparent and dimly to moderately clear. The Herderites are accompanied by a large number of very small Elbaite crystals that have a good form. They appear to have a very pale green coloration; this is difficult to see, though, as they are mostly covered with a thin crust of intergrown muscovite platelets. The albite base on which they rests is visibly crystalline, but shows no definable form.
her-6 ($ 45.00)
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
HERDERITE specimen her-7
$ 45.00
$ 45.00
Dims: 3.1 x 3.1 x 0.7" (7.9 x 7.9 x 1.8 cm)
Wt: 4.97 oz. (140.9 g)
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
This hand specimen is a lot like other Herderite specimens from this locality in the fact that it consists of at least 25 small crystals that rest on a crystalline albite base. These crystals are generally in good condition, though a few are obviously damaged or broken. The largest of these crystals measures 0.6" (1.5 cm) in length, and all have good monoclinic prismatic form, with well-defined edges and clean faces that possess a pearly luster. All have a very pale gray-green coloration and are translucent to dimly transparent, containing many internal fractures. The albite base on which they rest is crusted with hundreds of tiny muscovite formations that have an almost stalactitic appearance and are slightly rust-stained.
her-7 ($ 45.00)
Sabsir, Rondu District, Gilgit-Skardu Rd., Northern Areas, Pakistan
HERDERITE specimen her-8
$ 40.00
$ 40.00
Dims: 0.8 x 0.7 x 0.5" (2.0 x 1.8 x 1.3 cm)
Wt: 5.7 g
Chhappu, above Dassu, Northern Areas, Pakistan
At lest 12 small Herderite prisms are clustered to form this thumbnail specimen. Though a few of them are viaibly damaged, the cluster is basically in very good condition. The largest of these crystals has dimensions of 0.6 x 0.4 x 0.4" (1.5 x 1.0 x 1.0 cm) and like all of the others, has excellent monoclinic prismatic form, even considering its intergrowth- it has well-defined edges and clean faces that possess a luster that varies from waxy to pearly. All have a very pale gray-green coloration and are translucent because they contain many internal fractures and cloudy inclusions. There are a few broken muscovite "books" present, but no host or base rock.
her-8 ($ 40.00)
Chhappu, above Dassu, Northern Areas, Pakistan
HERDERITE specimen her-9
$ 38.00
$ 38.00
Dims: 2.4x2.1x2.0" (6.2x5.3x5.2 cm)
Wt: 3.6 oz. (101.6g)
Linopolis, Minas Gerais, Brazil
This hand specimen consists of dozens of small pale brown herderite crystals and two large muscovite books on an albite base. The herderite crystals are complex, showing many different shapes including prismatic with domal terminations. They appear transparent, although this is spoiled by many internal fractures. Close examination indicates that the herderite crystals are very pale yellow to colorless, and the pale brown color is from a brown cryst that lightly coats some crystals and crevices.
her-9 ($ 38.00)
Linopolis, Minas Gerais, Brazil