DOLOMITE
- Chemistry: CaMg(CO3)2, Calcium Magnesium Carbonate
- Class: Carbonates
- Group: Dolomite
- Uses: in some cements, as a source of magnesium and as mineral specimens.
Specimens
Dolomite in addition to the sedimentary beds is also found in metamorphic marbles, hydrothermal veins and replacement deposits. Except in its pink, curved crystal habit dolomite is hard to distinguish from its second cousin, calcite. But calcite is far more common and effervesces easily when acid is applied to it. But this is not the case with dolomite which only weakly bubbles with acid and only when the acid is warm or the dolomite is powdered. Dolomite is also slightly harder, denser and never forms scalenohedrons (calcite's most typical habit).
Dolomite differs from calcite, CaCO3, in the addition of magnesium ions to make the formula, CaMg(CO3)2. The magnesium ions are not the same size as calcium and the two ions seem incompatible in the same layer. In calcite the structure is composed of alternating layers of carbonate ions, CO3, and calcium ions. In dolomite, the magnesiums occupy one layer by themselves followed by a carbonate layer which is followed by an exclusively calcite layer and so forth. Why the alternating layers? It is probably the significant size difference between calcium and magnesium and it is more stable to group the differing sized ions into same sized layers. Other carbonate minerals that have this alternating layered structure belong to the Dolomite Group. Dolomite is the principle member of the Dolomite Group of minerals which includes ankerite, the only other somewhat common member.
Dolomite forms rhombohedrons as its typical crystal habit. But for some reason, possibly twinning, some crystals curve into saddle-shaped crystals. These crystals represent a unique crystal habit that is well known as classical dolomite. Not all crystals of dolomite are curved and some impressive specimens show well formed, sharp rhombohedrons. The luster of dolomite is unique as well and is probably the best illustration of a pearly luster. The pearl-like effect is best seen on the curved crystals as a sheen of light can sweep across the curved surface. Dolomite can be several different colors, but colorless and white are very common. However it is dolomite's pink color that sets another unique characteristic for dolomite. Crystals of dolomite are well known for their typical beautiful pink color, pearly luster and unusual crystal habit and it is these clusters that make very attractive specimens.
PHYSICAL CHARACTERISTICS:
- Color is often pink or pinkish and can be colorless, white, yellow, gray or even brown or black when iron is present in the crystal.
- Luster is pearly to vitreous to dull.
- Transparency crystals are transparent to translucent.
- Crystal System is trigonal; bar 3
- Crystal Habits include saddle shaped rhombohedral twins and simple rhombs some with slightly curved faces, also prismatic, massive, granular and rock forming. Never found in scalenohedrons.
- Cleavage is perfect in three directions forming rhombohedrons.
- Fracture is conchoidal.
- Hardness is 3.5-4
- Specific Gravity is 2.86 (average)
- Streak is white.
- Other Characteristics: Unlike calcite, effervesces weakly with warm acid or when first powdered with cold HCl.
- Associated Minerals: include calcite, sulfide ore minerals, fluorite, barite, quartz and occasionally with gold.
- Notable Occurrences include many localities throughout the world, but well known from sites in Midwestern quarries of the USA; Ontario, Canada; Switzerland; Pamplona, Spain and in Mexico.
- Best Field Indicators are typical pink color, crystal habit, hardness, slow reaction to acid, density and luster.
 Amethyst Galleries' Mineral Gallery MINERALS |
DOLOMITE specimen dol-1
$ 35.00
$ 35.00
Dims: 6-1/4" x 3-3/4" x 3"
Wt: 2 lbs., 7.6 oz
Black Rock, Arkansas, U.S.A.
One of the larger of our available Dolomite specimens, this one has the classic pink, curved crystals that are associated with localities near Hot Springs in Arkansas. The crystals are of a medium size(1/8 to 1/2 inch in length) and have clean rhombohedral forms with curved faces. There is considerable damage to the crystals on the edges of the cluster, but most are in pristine condition. A few tiny crystals of chalcopyrite make a home, but they are barely noticeable. More eye-catching are three pseudohexagonal prismatic crystals of calcite, one of which displays a double basal pinacoid termination, another of which shows considerable damage. These lovelies rest on the obligatory gray limestone base that is also very common for Arkansas material.
dol-1 ($ 35.00)
Black Rock, Arkansas, U.S.A.
DOLOMITE specimen dol-2
$ 20.00
$ 20.00
Dims: 3-1/2" x 2-1/4" x 1-3/8"
Wt: 4.2 oz
Indiana, U.S.A.
Dolomite specimens from Indiana are not all that easily found on the market, though they do not tend to be expensive. This specimen(sorry, exact locality unknown) has pale pink crystals with curved faces and edges like those from Arkansas, yet are not quite as large, and though a bit rougher in form, the crystals are for the most part undamaged and complete, with a good pearly luster. There are two excellent calcite crystals on the specimen, though, which are worth a second look. They are both in a trigonal prismatic crystal form with a hexagonal cross-section and basal pinacoid terminations. One measures over 5/8" in length, while the other approaches 1-1/4". The larger seems to have 3 spots on it that are just visible where the most exposed prism face meets its corresponding termination face, but these measure less than 1 mm in diameter, and so do not appreciably detract from the crystal. The other shows one similar spot on a termination about halfway down the crystal's length. They are not transparent, but have a very subtle yellow-white coloration.
dol-2 ($ 20.00)
Indiana, U.S.A.
DOLOMITE specimen dol-3
$ 40.00
$ 40.00
Dims: 3" x 1-3/4" x 1-1/8"
Wt: 2.18 oz
Vekol Mine, Pinal Co., Arizona, U.S.A.
I have not seen Dolomite occur in this nature before! It came to us under the name Ferroandolomite; David, our Geologist and general "fount of knowledge" said that we should classify it as a variety of Dolomite that has intense concentrations of included hematite. So be it! Needless to say, the crystals have the standard rhombohedral form with curved faces and edges of Dolomite, along with the pearly luster. However, the edges and faces are visibly straighter than those in regular Dolomite, and these have the rich, red-brown color of hematite powder. The largest of these crystals measures about 1/2" along an edge, and the smallest measures just under 1/4". There is no visible matrix rock. The entire cluster is covered with a light dusting of tiny, clear calcite crystals.
dol-3 ($ 40.00)
Vekol Mine, Pinal Co., Arizona, U.S.A.
DOLOMITE specimen dol-4
$ 30.00
$ 30.00
Dims: 5" x 3-1/4" x 3"
Wt: 1 lb., 11.2 oz
Black Rock, Arkansas, U.S.A.
There actually isn't a large number of complete Dolomite crystals on this particular specimen, but it is still very attractive. Those that are on the specimen have the classic pink color, short curved bladed form, and pearly luster of Dolomite from this locality. They achieve a maximum length of about 1/4 inch and are dusted lightly with tiny chalcopyrite crystals. There are also 2 calcite crystals; one is heavily cloven and incomplete, whereas the other has only minor damage and exceptional clarity and form, with a complex shape. Their color is a pale yellow. All of these rest on a matrix that is made up of damaged Dolomite crystals and gray limestone.
dol-4 ($ 30.00)
Black Rock, Arkansas, U.S.A.
DOLOMITE specimen dol-5
$ 35.00
$ 35.00
Dims: 2-1/2" x 1-7/8" x 1-1/2"
Wt: 3.6 oz
Mt. Brussilof Mine(near Radium), British Columbia, Canada
I would have put this specimen under the "magnesite" specimen list because of the supposed rarity of it in crystal form, but I thought the Dolomite crystals on the piece were so much neater! There are 3 of these crystals that I can detect on the specimen, and they make up the bulk of it, being surrounnded by several curved and sharply-edged tablets of white magnesite. Ergo, the Dolomite crystals are quite large, one spanning over 1 inch across a secondary face. Their most impressive trait stems from the fact that they are colorless(no pink stuff here!) and they are incredibly clear. One can see internal fractures with close scrutiny-- on a first glance, one would think that it is actually Iceland spar calcite! All three crystals show noticeable damage(the largest having the least, surprisingly) and may have been cleaved in some spots, due to the fact that some faces show an almost vitreous luster, while most of the undamaged ones show more of a pearly luster. There is no attached host rock, and the underside of the specimen is full of more Dolomite, heavily cloven(cleaved).
dol-5 ($ 35.00)
Mt. Brussilof Mine(near Radium), British Columbia, Canada
DOLOMITE specimen dol-6$ 70.00
Dims: 1-3/4" x 1-3/4" x 1/2"
Wt: 1.67 oz. w/ base
Mt. Brussilof Mine(near Radium), British Columbia, Canada
This specimen amazes me. Read the weight and the dimensions of it. Now, realize that the entire specimen is one single crystal! It's by far the largest individual Dolomite crystal that I have held in my hand. It has excellent, though interrupted, crystal form, a small amount of exterior damage for a crystal its size, and a pearly luster. Ah, yes, did I mention that it is colorless and apart from much internal fracturing, transparent?? I was wondering if it was actually twinned, but I'm pretty sure that it is an individual. There are one or two tiny, damaged clusters of magnesite on one side of the tablet; the specimen is attached to a small(tot. wt. approx. 10.5 g) acrylic base for display.
dol-6 ($ 70.00)Mt. Brussilof Mine(near Radium), British Columbia, Canada
DOLOMITE specimen dol-7
$ 20.00
$ 20.00
Dims: 2-3/4" x 2-3/4" x 1-1/2"
Wt: 3.3 oz
Mt. Brussilof Mine(near Radium), British Columbia, Canada
I count at least 7 distinct Dolomite crystals on this specimen. They all show good formation, though incomplete, and have a pearly luster on some faces and an almost vitreous luster on others; there is damage on every crystal, and likely some cleaving evidence. All of them are colorless and have unusually good clarity, approaching transparency. There is no matrix rock, although in two spots there is a dusting of what I think are microscopic platelets of magnesite.
dol-7 ($ 20.00)
Mt. Brussilof Mine(near Radium), British Columbia, Canada
DOLOMITE specimen dol-8
$ 25.00
$ 25.00
Dims: 1.5" x 1.4" x 0.8"(3.8 x 3.6 x 2.0 cm)
Wt: 19.8 g w/ base
Mt. Brussilof Mine(near Radium), British Columbia, Canada
Though they do show some noticeable damage, the two Dolomite crystals on this specimen exhibit good form and excellent clarity. They are colorless and have a pearly luster, and occur in what appear to be rhombohedral prisms. They are interpenetrating, but probably not twinned. The larger of the two measures 0.8 x 0.5 x 0.4"(2.0 x 1.3 x 1.0 cm), and the smaller has visible dimensions of 0.5 x 0.3"(1.3 x 0.8 cm). They both contain phantoms made up of a white material, and the larger crystal has some unusually dark veil-like inclusions. These crystals rest on a bed of magnesite crystals that occur as thin tabular blades with curved edges. They have a thin, milky-white color, silky luster, and show dim transparence. The specimen is hot-glued onto an acrylic base.
dol-8 ($ 25.00)
Mt. Brussilof Mine(near Radium), British Columbia, Canada
DOLOMITE specimen dol-9
$ 25.00
$ 25.00
Dims: 2.5 x 1.7 x 1.0" (6.4 x 4.3 x 2.5 cm)
Wt: 1.94 oz. (54.9 g)
1240 Bench, Rabbit Lake Mine, Wollaston Lake, Saskatchewan, Canada
Scores of Dolomite crystals are intergrown to make up this small hand specimen. The crytals range in size from 2 mm to 0.6" (1.5 cm) along an edge and have excellent rhombohedral form, with straight, sharp edges and flat faces that possess a rather dull pearly-to-waxy luster. The crystals are generally in good condition, though some of the larger ones are obviously damaged and one is broken and mostly incomplete. All have a gray coloration with a hint of rusty pink, and are completely opaque. Their color is caused by a thin shell of colored dolomite that has coated the crystals, which also is the cause of their opacity. One can see from the broken crystal that most of the mass of each consists of nearly transparent, milky-white dolomite. There is no host rock of any sort present.
dol-9 ($ 25.00)
1240 Bench, Rabbit Lake Mine, Wollaston Lake, Saskatchewan, Canada
DOLOMITE specimen dol-10
$ 33.00
$ 33.00
Dims: 2.4 x 2.2 x 1.6" (6.1 x 5.6 x 4.1 cm)
Wt: 3.97 oz. (112.5 g)
1240 Bench, Rabbit Lake Mine, Wollaston Lake, Saskatchewan, Canada
Several dozen Dolomite crystals are clustered together to make up this specimen. These crystals vary widely in size, from less than 0.1" (3 mm) along any axis to 0.6 x 0.3 x 0.3" (1.5 x 0.8 x 0.8 cm) and are generally in moderately good condition, as several of the crystals are obviously damaged and most of these are incomplete. Where intact, however, they have excellent rhombohedral form, with sharp edges and relatively clean faces that possess a dull pearly luster. All have a pale red-brown coloration with a hint of pink on their undamaged surfaces and appear to be opaque, but those that are damaged show interiors with a pale violet or even a milky-white coloration. This core material is also translucent and dimly transparent in some areas, as internal fractures are visible beneath the surface. The cluster has a hollow, almost nodular formation- its lower surface is concave and lined with many tiny quartz prisms that partly coat the Dolomite. There is no host rock present, however.
dol-10 ($ 33.00)
1240 Bench, Rabbit Lake Mine, Wollaston Lake, Saskatchewan, Canada
DOLOMITE specimen dol-11
$ 55.00
$ 55.00
Dims: 2.4 x 2.2 x 0.9" (6.1 x 5.6 x 2.3 cm)
Wt: 3.06 oz. (86.8 g) w/ base
Mount Brussilof, near Radium, British Columbia, Canada
This rather simple specimen consists of what appears to be an incomplete, twinned Dolomite crystal. Close examination, however, will show that the crystal is not twinned, and a convenient notch in one edge simply gives it that appearance. Thus, it is simply part of a large rhombohedron that shows excellent form, with well-defined edges and very clean faces that possess an almost vitreous luster. The crystal is white and basically cloudy, though small portions of clarity extend well into it. There is no host rock present, but a single quartz crystal is slightly embedded into one side edge. The piece is hot-glued onto a flat, square acrylic base.
dol-11 ($ 55.00)
Mount Brussilof, near Radium, British Columbia, Canada
DOLOMITE specimen dol-12
$ 40.00
$ 40.00
Dims: 2.3 x 1.5 x 1.3" (5.9 x 3.8 x 3.2 cm)
Wt: 2.5 oz. (71 g)
Eagle Mine, Gilman, Eagle County, Colorado, U.S.A.
A cluster of several large, intersecting Dolomite crystals makes up this specimen. The crystals are in moderately good condition, as much damage is visible, and reach dimensions of 0.4 x 0.4 x 0.2" (1.1 x 1.1 x 0.6 cm). Their trigonal-based rhombohedral form is good, though slightly warped in some spots, and all hvae a pale brown color and a dull luster that appear to be caused by a crust that coats them. Where damaged, this crust is removed to reveal a pale gray interior with a waxy luster. The brown material is essentially opaque, but the gray interior is likely translucent. The Dolomites are accompanied by many tiny pyrite and galena crystals. Glue is visible on one side of the specimen, though I cannot determine where any damage occurred that would be repaired.
dol-12 ($ 40.00)
Eagle Mine, Gilman, Eagle County, Colorado, U.S.A.
DOLOMITE specimen dol-13
$ 75.00
$ 75.00
Dims: 2.0 x 1.8 x 1.6" (5.2 x 4.5 x 4.0 cm)
Wt: 2.9 oz. (81 g)
Eagle Mine, Gilman, Colorado, U.S.A.
This lovely hand specimen consists primarily of a cluster of many intergrown Dolomite rhombohedra. These crystals reach dimensions of 0.8 x 0.7 x 0.6" (1.9 x 1.8 x 1.5 cm) and only a few are noticeably damaged. Their trigonal-based form is likewise excellent, and all have a dull, milky-white color and a dull, waxy luster. They are translucent and cloudy, and each appears to contain many internal cleavage planes. Scores of tiny tetrahedrite crystals rest on the Dolomites- they are in good condition and have good tetrahedral form, though most are intergrown into small clusters. A small amount of a granular dolomite/pyrite base is present.
dol-13 ($ 75.00)
Eagle Mine, Gilman, Colorado, U.S.A.
DOLOMITE specimen dol-14
$ 115.00
$ 115.00
Dims: 3.2 x 2.4 x 1.8" (8.0 x 6.0 x 4.5 cm)
Wt: 4.1 oz. (116 g)
Rayas Mine, Guanajuato, Guanajuato, Mexico
A single, very large Dolomite tablet rests on the crystalline quartz base of this small cabinet specimen. This blade is in good condition, showing no fresh damage, and has dimensions of 2.3 x 2.2 x 0.8" (5.8 x 5.6 x 1.9 cm). Though it has a faintly definable trigonal tabular form, it has undergone intense weathering- a few tiny spots show excellent luster and crystalline striations, but the rest of its surface is rough and jagged. A few other, tiny Dolomite tablets rest elsewhere on the base, but these are small and most are broken. The base itself is made up entirely of intergrown quartz crystals that are in good condition and have excellent form.
dol-14 ($115.00)
Rayas Mine, Guanajuato, Guanajuato, Mexico
DOLOMITE specimen dol-15
$ 102.00
$ 102.00
Dims: 3.3 x 3.0 x 1.1" (8.3 x 7.6 x 2.8 cm)
Wt: 7.7 oz. (219 g)
Black Cloud Mine, Leadville, Colorado, U.S.A.
This cabinet piece consists of a galena crust that is coated with a crust made up of hundreds of intergrown Dolomite crystals. These crystals are generally in very good condition and reach diameters of 0.5" (1.3 cm). All have excellent rhombohedral form with slightly curved faces and edges, a white color and a dull pearly luster. Some are coated with a thin, dull, gray crust. The galena base is made up of countless tiny, intergrown cubes, and a considerable amount of crystalline pyrite is present.
dol-15 ($102.00)
Black Cloud Mine, Leadville, Colorado, U.S.A.
DOLOMITE specimen dol-16
$ 57.00
$ 57.00
Dims: 1.4 x 1.2 x 0.8" (3.6 x 3.1 x 2.0 cm)
Wt: 14 g
Tormiq, above Baghicha, Gilgit-Skardu Rd., Northern Areas, Pakistan
A very odd cluster of apparently worn Dolomite makes up the bulk of this small hand specimen. Between the wear and the intergrowth, it is difficult to determine definite crystals there are definite crystalline faces and edges visible, though. None of the material is damaged. The Dolomite has a greenish-yellow color and a dull pearly-to-waxy luster, and is translucent. A small amount of broken, crystalline quartz is attached to the formation.
dol-16 ($ 57.00)
Tormiq, above Baghicha, Gilgit-Skardu Rd., Northern Areas, Pakistan
DOLOMITE specimen dol-17
$ 25.00
$ 25.00
Dims: 1.6 x 1.3 x 1.1" (4.0 x 3.3 x 2.7 cm)
Wt: 1.4 oz. (39 g) w/ base
Mount Saint Hilaire, Quebec, Canada
A crust of crystalline Dolomite fills the space between two pieces of the shale base of this hand specimen. The crystals that make up the crust do not exceed 0.2" (5 mm) in diameter and are generally in good condition, though portions of the crust are damaged. All have a rhombohedral form that is nearly cubic in appearance, and their pale green color is an unusual contrast to their standard pearly luster. They all show dim transparence. The piece is hot-glued to a flat, square acrylic base.
dol-17 ($ 25.00)
Mount Saint Hilaire, Quebec, Canada