THE MINERAL DATOLITE

  • Chemistry: CaBSiO4(OH), Calcium Boron Silicate Hydroxide.
  • Class: Silicates
  • Subclass: Nesosilicates
  • Group: Datolite
  • Uses: As a mineral specimen, rarely as an ornamental stone and as a minor gemstone.
  • Specimens
Datolite is a popular mineral among mineral collectors although it is somewhat obscure. It forms nicely faceted complex crystals. The crystals at first glance could appear to be other crystal forms such as the isometric dodecahedron or trapezohedron. However these highly symmetric crystal forms are easily distinguished from the crystals of datolite. Datolite's crystals although usually well formed and strickingly faceted lack any symmetry elements except for one mirror plane and one axis of two fold rotation.

Datolite is often found in basalt vesicles with calcite and zeolites. In fact, it is often confused with certain zeolites because of its luster, color and associations. Datolite is also found in the Lake Superior region of Michigan. It is associated with native copper at this location and is found in porcelain-like masses and nodules. The nodules are brown to off white in color and some are cut and polished as a ornamental stone.

PHYSICAL CHARACTERISTICS:

  • Color is white, colorless, yellowish, reddish, gray, brown and green.
  • Luster is vitreous to greasy.
  • Transparency: Crystals are transparent to translucent.
  • Crystal System: Monoclinic; 2/m
  • Crystal Habits include short prismatic to wedge shaped tabular crystals with complex and richly faceted terminations. Also in porcelain-like masses that form nodules. Aggregates can be fibrous or granular.
  • Cleavage is absent.
  • Fracture is conchoidal to uneven.
  • Hardness is 5 - 5.5
  • Specific Gravity is 2.8 - 3.0
  • Streak is white.
  • Associated Minerals are prehnite, danburite, babingtonite, epidote, copper, calcite, quartz and zeolites.
  • Notable Occurances include Russia; Lake Superior region of Michigan and Paterson, New Jersey, USA; Bancroft, Ontario, Canada; Charcas, Mexico; Schwarzwald, Germany and Norway.
  • Best Field Indicators are crystal habit, absence of cleavage, hardness and color.
DATOLITE specimens:
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DATOLITE specimen dat-1
$ 225.00
Dims: 3.3" x 2.3" x 1.4" (8.4 x 5.8 x 3.6 cm)
Wt: 5.79 oz. (164.0 g)
Verchniy Quarry, Dal'negorsk, Primorskiy Kray, C.I.S., Russia
Three individual Datolite crystals rise above the quartz and calcite base of this specimen. The largest of these has dimensions of 2.3 x 1.0 x 0.9" (5.8 x 2.5 x 2.3 cm), and the others are less than half that size. They occur as rather thick monoclinic prismatic crystals that have a pearly luster, and they have a pale green color and are transparent and moderately clear in some areas, though they contain many internal fractures and flaws. There is only a very small amount of visible damage to the crystals, which are all at least partially coated with a thin druse of tiny, intergrown, clear quartz crystals. The base on which the Datolites rest is made up of several clear, hexagonal prismatic quartz crystals that have a matte luster and many shards of calcite that represent broken, bladed crystals.
no photo
dat-1 ($225.00)
Verchniy Quarry, Dal'negorsk, Primorskiy Kray, C.I.S., Russia
DATOLITE specimen dat-2
$ 20.00
Dims: 1.9" x 1.6" x 0.8" (4.8 x 4.1 x 2.0 cm)
Wt: 1.11 oz. (31.6 g)
Poona, Maharashtra State, India
One of the more unusual forms of Datolite, this specimen represents a massive form that the mineral takes on rare occasions. There are several other materials in the specimen, though, including a substantial amount of quartz and maybe a bit of basalt rock. One face has been cut into the piece to make viewing easier. The Datolite occurs in an oolitic form, with a color that ranges from an opaque, dark, brick-red to a nearly transparent colorlessness. There is also some material that has the grassy, yellow-green color of pyromorphite, though I am sure that that is not what the material is.
no photo
dat-2 ($ 20.00)
Poona, Maharashtra State, India
DATOLITE specimen dat-3
$ 80.00
Dims: 2.3" x 1.9" x 0.9" (5.8 x 4.8 x 2.3 cm)
Wt: 1.83 oz. (51.8 g)
La Aurora Mine, Charcas, San Luis Potosi, Mexico
I was surprised at first of the locality of this specimen, but as it is sometimes associated with danburite, I could understand. It consists of a very thin, pyrite-laden crust which is coated with a crust made up of several monoclinic prismatic Datolite crystals. These crystals range in length from 0.1 - 0.6" (0.3 - 1.5 cm) and are all incomplete due either to intergrowth or to the fact that they all have grown out at acute angles; one of the larger crystals appears to have grown nearly parallel to the underlying crust. All the crystals have well-defined edges and smooth faces that show a waxy-to-pearly luster. Their color is a pale green, which is rather common for this mineral. They appear to be transparent and clear to a degree, though the larger crystals are merely translucent due to cloudy inclusions and probable internal fracturing. Scattered on the Datolite cluster are tiny clusters of almost microscopic, white crystals. I do not know what they are, and they are too small for me to effectively discern their crystal form, even under 10-power magnification.
no photo
dat-3 ($ 80.00)
La Aurora Mine, Charcas, San Luis Potosi, Mexico
DATOLITE specimen dat-4
$ 60.00
Dims:2.7x1.9x1.1" (6.9x4.8x2.8 cm)
Wt: 3.5oz. (98g)
Delaware Mine, Keweenaw cty., Michigan
This is a nodule of datolite that has been cut and polished on one side. The polished side shows the light to dark brown datolite, light gray impurities, and an interesting spider-web effect of fissures that were filled with a dark colored material. The exterior face shows the nodular form of the datolite.
no photo
dat-4 ($ 60.00)
Delaware Mine, Keweenaw cty., Michigan
DATOLITE specimen dat-5
$ 25.00
Dims:1.4x0.9x0.5" (3.6x2.3x1.3 cm)
Wt: 0.4oz. (12g)
Knowlton Lode, Caledonia Mine, Ontonagon cty., Michigan
This specimen consists of a nodule of massive datolite that has been partially polished. There are faint banding marks visible on the polished section showing that the datolite was deposited in layers. There is a thin vein of copper along the bottom of the nodule. This specimen is undamaged.
no photo
dat-5 ($ 25.00)
Knowlton Lode, Caledonia Mine, Ontonagon cty., Michigan
DATOLITE specimen dat-6
$ 39.00
Dims:1.3x1.1x0.3" (3.3x2.8x0.8 cm)
Wt: 0.9oz. (26g)
Delaware Mine, Keweenaw cty., Michigan
This is a two-piece specimen. It consists of two pieces of a nodule of datolite that has been cut and polished on one side. The two pieces do not match-they are from seperate nodules, or perhaps each side of a larger nodule. One side on each piece has been broken away. There is some iron staining visible in the polished sides.
no photo
dat-6 ($ 39.00)
Delaware Mine, Keweenaw cty., Michigan
DATOLITE specimen dat-7
$ 100.00
Dims: 5.19x3.30x2.05" (13.19x8.39x5.21cm)
Wt: 19.43oz (550g)
Dalnyegorsk, Russia
This is a very nice cabinet specimen of datolite. It has a complex shape and is likely three or more intergrown crystals. It is pale green with a vitreous luster, and is translucent. Some surfaces are slightly dulled by tiny pits, while others show interesting growth patterns. Some of the pits have a dark filler, and parts of the bottom and a side appear dirty.
no photo
dat-7 ($100.00)
Dalnyegorsk, Russia
 

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