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Brucite is most often in crude, uninteresting form, but several localities produce distinct and interesting crystals which are highly desirable to collectors. Brucite may form as a standalone mineral, but it can also form as layers within minerals of the chlorite group and clay minerals such as Montmorillonite and Smectite. It forms a component of certain types of marbles, which are commercially known as pearl grey marble. Brucite is named in honor of Archibald Bruce (1777-1818), a mineralogist who first described this mineral. |
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Chemical Formula |
Mg(OH)2 |
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Composition |
Magnesium hydroxide, often with some iron and manganese |
| Variable Formula |
(Mg,Fe,Mn)(OH)2 |
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Color |
White, colorless, cream, gray, light yellow, grayish-blue, blue, green, greenish-blue, light red, pink |
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Streak |
White |
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Hardness |
2 - 2.5 |
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Crystal System |
Hexagonal |
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Crystal Forms
and Aggregates |
As thin tabular plates and groups of such crystals, in foliated masses, scaly, lamellar, bladed, fibrous, grainy, and massive. May also form as rounded crystal masses, botryoidal, in rounded, ball-like spheres, and with rosette formations. |
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Transparency |
Transparent to translucent |
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Specific Gravity |
2.3 - 2.4 |
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Luster |
Vitreous. Pearly on cleavage faces. |
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Cleavage |
1,1 |
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Fracture |
Uneven |
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Tenacity |
Sectile, slightly flexible but inelastic |
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Other ID Marks |
May fluoresce blue. |
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In Group |
Oxides; Hydroxides |
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Striking Features |
Sectility |
| Environment |
In Serpentine deposits, marble, and in Nepheline syenite pegmatites. |
| Rock Type |
Igneous, Metamorphic |
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Popularity (1-4)
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2 |
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Prevalence (1-3)
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2 |
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Demand (1-3) |
2 |
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Brucite is used as a source of magnesium, and is also mined for a Brucite marble. Large individual crystals ans well-formed crystal groups are rare and desirable collector's minerals, especially those from the defunct Wood's Chrome Mine in Pennsylvania.
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Although Brucite is generally a common mineral, specimens worthy of collection only come from a handful of locations worldwide. In Italy, light blue crystal plates have come from the Val di Serra Quarry, Pilcante, Trento Province, Italy. The Kalahari manganese field, in Northern Cape Province, South Africa has produced exceptional examples of Brucite. This includes botryoidal aggregates and rounded, ball-like crystals of all colors at the N'Chwaning Mines at Kuruman; and blue and yellow Brucite in rounded crystal masses from the Wessels Mine, at Hotazel. A new find of bright yellow Brucite from the Killa Saifullah District, Balochistan, Pakistan, has recently popularized this mineral, with an abundance of exceptionally-colored rounded crystal groups that have redefined this mineral for collectors.
In the U.S., Brucite was first described from Castle Hill, Hoboken, Hudson Co., New Jersey, the type locality also known for the presence of its Nemalite variety. One of the most classic localities for this mineral is Wood's Chrome Mine, Texas, Lancaster Co., Pennsylvania, where some of the largest crystals of Brucite were found. Excellent crystals also come from the nearby Cedar Hill Quarry, Fulton Township, Lancaster Co., Pennsylvania. Good Brucite crystals are found at the Sierra Magnesite Mine, Gabbs, Nye Co., Nevada. In Canada, foliated crystal plates have come from the Maxwell quarry, Wakefield, Québec.
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The characteristics of Brucite can usually distinguish it from other minerals. However, it can have similar properties to Gypsum, but the crystal habits are usually very different.
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Have a question about Brucite? Visit our Q&A Community and ask the experts!
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