Brack Gem prospect (Brack prospect), East Glastonbury, Glastonbury, Hartford Co., Connecticut, USAi
| Regional Level Types | |
|---|---|
| Brack Gem prospect (Brack prospect) | Prospect |
| East Glastonbury | - not defined - |
| Glastonbury | - not defined - |
| Hartford Co. | County |
| Connecticut | State |
| USA | Country |
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Key
Latitude & Longitude (WGS84):
41° 38' 60'' North , 72° 31' 0'' West
Latitude & Longitude (decimal):
Locality type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Terramuggus | 1,025 (2017) | 4.2km |
| Lake Pocotopaug | 3,436 (2017) | 5.8km |
| East Hampton | 2,691 (2017) | 8.3km |
| Glastonbury Center | 7,387 (2017) | 8.9km |
| Glastonbury | 31,876 (2017) | 10.3km |
Decomposed lithium-rich granite pegmatite. Unlike other pegmatites in this region, this one has completely decomposed feldspar, with "nests" of pocket contents occurring loose in soft clay. According to Jarnot (1995) it produced some of the finest colored gem elbaite and gem beryl from the state.
The "quarry" is no longer evident and only dirt dumps are obvious. Barton and Goldsmith (1968) provides a description of this weathered, gem-rich pegmatite that was hand-worked by the Brack family from 1958 to 1963 but is now abandoned:
The Brack prospect....is on a 71-acre tract owned by Arthur and Walter Brack of East Hampton. It is a gravel pit in the crest of a residually weathered rare-alkali pegmatite. It was being worked on weekends by the owner in 1963. Workings consisted of an irregular oval pit 150 by 75 feet in plan and 5 to 10 feet deep.
The fresh pegmatite was not exposed but the weathered material appears to be approximately in its original attitude and appears to strike northeast and dip 20° to 25° NW. It is on the crest of a ridge beneath up to 5 feet of glacial sand and gravel. Weathered mica and feldspar have shown up in test pits for 300 feet along strike. Feldspar has weathered mostly to kaolin leaving lepidolite, muscovite, quartz, beryl, and tourmaline of many colors, and some rotted cleavelandite as gravel. Some of the finest beryl and watermelon tourmaline crystals ever found in New England have been recovered. The approximately 1,000 pounds of beryl and 250 pounds of tourmaline that have been hand-sorted included approximately 200 pounds of beryl and 25 pounds of tourmaline of faceting grade. A gin pole with a 50-foot boom and ¼-ton bucket has been used to excavate the pit. It is operated by a hand winch. Screens, hand shovels, and buckets of wash water are the only other equipment used. As near as can be determined, beryl has constituted less than 0.5 percent of the material excavated to the time of this examination.
The fresh pegmatite was not exposed but the weathered material appears to be approximately in its original attitude and appears to strike northeast and dip 20° to 25° NW. It is on the crest of a ridge beneath up to 5 feet of glacial sand and gravel. Weathered mica and feldspar have shown up in test pits for 300 feet along strike. Feldspar has weathered mostly to kaolin leaving lepidolite, muscovite, quartz, beryl, and tourmaline of many colors, and some rotted cleavelandite as gravel. Some of the finest beryl and watermelon tourmaline crystals ever found in New England have been recovered. The approximately 1,000 pounds of beryl and 250 pounds of tourmaline that have been hand-sorted included approximately 200 pounds of beryl and 25 pounds of tourmaline of faceting grade. A gin pole with a 50-foot boom and ¼-ton bucket has been used to excavate the pit. It is operated by a hand winch. Screens, hand shovels, and buckets of wash water are the only other equipment used. As near as can be determined, beryl has constituted less than 0.5 percent of the material excavated to the time of this examination.
According to Susan (Brack) Boulanger, she and her sister still own the prospect in 2012.
Select Mineral List Type
Standard Detailed Strunz Dana Chemical ElementsDetailed Mineral List:
| ⓘ Albite Formula: Na(AlSi3O8) Habit: massive Description: Mostly weathered away to clays Reference: Van King |
| ⓘ Albite var: Cleavelandite Formula: Na(AlSi3O8) Description: mostly weathered away to clays Reference: Barton and Goldsmith (1968) |
| ⓘ Beryl Formula: Be3Al2(Si6O18) Reference: Rocks & Min.: 70:379 |
| ✪ Beryl var: Aquamarine Formula: Be3Al2Si6O18 Colour: blue Description: good gem material found Reference: Rocks & Min.: 70:379
Jarnot (1995) |
| ✪ Beryl var: Goshenite Formula: Be3Al2(Si6O18) Habit: hexagonal prisms Colour: colorless Description: a gem quality flattened crystal 8 cm in diameter retained by Brack family. Reference: Rocks & Min.: 70:379 |
| ✪ Beryl var: Morganite Formula: Be3Al2(Si6O18) Colour: pink to peach Reference: Rocks & Min.: 70:379 |
| ⓘ Cassiterite Formula: SnO2 Reference: Rocks & Min.: 70:398
Jarnot (1995) |
| ⓘ 'Columbite-(Fe)-Columbite-(Mn) Series' Reference: Jarnot (1995) |
| ⓘ Cookeite Formula: (Al2Li)Al2(AlSi3O10)(OH)8 Habit: botryoidal aggregates of platy crystals Colour: pale yellow to gray Description: associated with elbaite, lepidolite, beryl Reference: Van King |
| ✪ Elbaite Formula: Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) Habit: elongated prisms Colour: green, pink, red Description: all elbaite crystals have a thin blue cap on the pedion termination, with "watermelon" crystals and gem nodules to 5 mm common Reference: Rocks & Min.: 70:379; Rocks & Minerals (1995) 70:396-409; Jarnot (1995) |
| ⓘ Kaolinite Formula: Al2(Si2O5)(OH)4 Colour: white Description: most of the feldspar has weathered to this clay. Reference: Jarnot (1995) |
| ⓘ 'Lepidolite' Habit: "ball-peen" aggregates Colour: gray to lavender Reference: Rocks & Min.: 70:379; Rocks & Minerals (1995) 70:396-409 |
| ⓘ Microcline Formula: K(AlSi3O8) Reference: Van King |
| ⓘ 'Microlite Group' Formula: A2-mTa2X6-wZ-n Reference: Rocks & Min.: 70:398 |
| ⓘ Muscovite Formula: KAl2(AlSi3O10)(OH)2 Reference: Van King |
| ⓘ Quartz Formula: SiO2 Reference: Rocks & Minerals (1995) 70:396-409 |
| ⓘ Quartz var: Smoky Quartz Formula: SiO2 Habit: prismatic with rhombic terminations Colour: gray to brown Description: associated with gem crystals Reference: Rocks & Min.: 70:379 |
| ⓘ Spessartine Formula: Mn2+3Al2(SiO4)3 Reference: Jarnot (1995) |
| ⓘ Staurolite Formula: Fe2+2Al9Si4O23(OH) Reference: Jarnot (1995) |
| ✪ 'Tourmaline' Formula: A(D3)G6(Si6O18)(BO3)3X3Z Habit: elongated prisms Colour: red to pink Description: typically with blue color "cap" on the pedion Reference: Rocks & Min.: 70:379 |
| ✪ 'Tourmaline var: Rubellite' Formula: A(D3)G6(T6O18)(BO3)3X3Z Habit: elongated prisms Colour: red to pink Description: typically with blue color "cap" on the pedion Reference: Rocks & Min.: 70:379 |
List of minerals arranged by Strunz 10th Edition classification
| Group 4 - Oxides and Hydroxides | |||
|---|---|---|---|
| ⓘ | Cassiterite | 4.DB.05 | SnO2 |
| ⓘ | 'Microlite Group' | 4.00. | A2-mTa2X6-wZ-n |
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| ⓘ | var: Smoky Quartz | 4.DA.05 | SiO2 |
| Group 9 - Silicates | |||
| ⓘ | Albite | 9.FA.35 | Na(AlSi3O8) |
| ⓘ | var: Cleavelandite | 9.FA.35 | Na(AlSi3O8) |
| ⓘ | Beryl | 9.CJ.05 | Be3Al2(Si6O18) |
| ⓘ | var: Aquamarine | 9.CJ.05 | Be3Al2Si6O18 |
| ⓘ | var: Goshenite | 9.CJ.05 | Be3Al2(Si6O18) |
| ⓘ | var: Morganite | 9.CJ.05 | Be3Al2(Si6O18) |
| ⓘ | Cookeite | 9.EC.55 | (Al2Li)Al2(AlSi3O10)(OH)8 |
| ⓘ | Elbaite | 9.CK.05 | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| ⓘ | Kaolinite | 9.ED.05 | Al2(Si2O5)(OH)4 |
| ⓘ | Microcline | 9.FA.30 | K(AlSi3O8) |
| ⓘ | Muscovite | 9.EC.15 | KAl2(AlSi3O10)(OH)2 |
| ⓘ | Spessartine | 9.AD.25 | Mn2+3Al2(SiO4)3 |
| ⓘ | Staurolite | 9.AF.30 | Fe2+2Al9Si4O23(OH) |
| Unclassified Minerals, Rocks, etc. | |||
| ⓘ | 'Columbite-(Fe)-Columbite-(Mn) Series' | - | |
| ⓘ | 'Lepidolite' | - | |
| ⓘ | 'Tourmaline' | - | A(D3)G6(Si6O18)(BO3)3X3Z |
| ⓘ | 'var: Rubellite' | - | A(D3)G6(T6O18)(BO3)3X3Z |
List of minerals arranged by Dana 8th Edition classification
| Group 4 - SIMPLE OXIDES | |||
|---|---|---|---|
| AX2 | |||
| ⓘ | Cassiterite | 4.4.1.5 | SnO2 |
| Group 8 - MULTIPLE OXIDES CONTAINING NIOBIUM,TANTALUM OR TITANIUM | |||
| A2B2O6(O,OH,F) | |||
| ⓘ | 'Microlite Group' | 8.2.2.1 | A2-mTa2X6-wZ-n |
| Group 51 - NESOSILICATES Insular SiO4 Groups Only | |||
| Insular SiO4 Groups Only with cations in [6] and >[6] coordination | |||
| ⓘ | Spessartine | 51.4.3a.3 | Mn2+3Al2(SiO4)3 |
| Group 52 - NESOSILICATES Insular SiO4 Groups and O,OH,F,H2O | |||
| Insular SiO4 Groups and O, OH, F, and H2O with cations in [4] and >[4] coordination | |||
| ⓘ | Staurolite | 52.2.3.1 | Fe2+2Al9Si4O23(OH) |
| Group 61 - CYCLOSILICATES Six-Membered Rings | |||
| Six-Membered Rings with [Si6O18] rings; possible (OH) and Al substitution | |||
| ⓘ | Beryl | 61.1.1.1 | Be3Al2(Si6O18) |
| Six-Membered Rings with borate groups | |||
| ⓘ | Elbaite | 61.3.1.8 | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings | |||
| Sheets of 6-membered rings with 2:1 layers | |||
| ⓘ | Muscovite | 71.2.2a.1 | KAl2(AlSi3O10)(OH)2 |
| Sheets of 6-membered rings interlayered 1:1, 2:1, and octahedra | |||
| ⓘ | Cookeite | 71.4.1.2 | (Al2Li)Al2(AlSi3O10)(OH)8 |
| Group 75 - TECTOSILICATES Si Tetrahedral Frameworks | |||
| Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si | |||
| ⓘ | Quartz | 75.1.3.1 | SiO2 |
| Group 76 - TECTOSILICATES Al-Si Framework | |||
| Al-Si Framework with Al-Si frameworks | |||
| ⓘ | Albite | 76.1.3.1 | Na(AlSi3O8) |
| ⓘ | Microcline | 76.1.1.5 | K(AlSi3O8) |
| Unclassified Minerals, Mixtures, etc. | |||
| ⓘ | Albite var: Cleavelandite | - | Na(AlSi3O8) |
| ⓘ | Beryl var: Aquamarine | - | Be3Al2Si6O18 |
| ⓘ | var: Goshenite | - | Be3Al2(Si6O18) |
| ⓘ | var: Morganite | - | Be3Al2(Si6O18) |
| ⓘ | 'Columbite-(Fe)-Columbite-(Mn) Series' | - | |
| ⓘ | Kaolinite | - | Al2(Si2O5)(OH)4 |
| ⓘ | 'Lepidolite' | - | |
| ⓘ | Quartz var: Smoky Quartz | - | SiO2 |
| ⓘ | 'Tourmaline' | - | A(D3)G6(Si6O18)(BO3)3X3Z |
| ⓘ | 'var: Rubellite' | - | A(D3)G6(T6O18)(BO3)3X3Z |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| H | ⓘ Cookeite | (Al2Li)Al2(AlSi3O10)(OH)8 |
| H | ⓘ Staurolite | Fe22+Al9Si4O23(OH) |
| H | ⓘ Kaolinite | Al2(Si2O5)(OH)4 |
| H | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Li | Lithium | |
| Li | ⓘ Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| Li | ⓘ Cookeite | (Al2Li)Al2(AlSi3O10)(OH)8 |
| Be | Beryllium | |
| Be | ⓘ Beryl (var: Morganite) | Be3Al2(Si6O18) |
| Be | ⓘ Beryl (var: Aquamarine) | Be3Al2Si6O18 |
| Be | ⓘ Beryl (var: Goshenite) | Be3Al2(Si6O18) |
| Be | ⓘ Beryl | Be3Al2(Si6O18) |
| B | Boron | |
| B | ⓘ Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| B | ⓘ Tourmaline (var: Rubellite) | A(D3)G6(T6O18)(BO3)3X3Z |
| B | ⓘ Tourmaline | A(D3)G6(Si6O18)(BO3)3X3Z |
| O | Oxygen | |
| O | ⓘ Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| O | ⓘ Beryl (var: Morganite) | Be3Al2(Si6O18) |
| O | ⓘ Beryl (var: Aquamarine) | Be3Al2Si6O18 |
| O | ⓘ Beryl (var: Goshenite) | Be3Al2(Si6O18) |
| O | ⓘ Tourmaline (var: Rubellite) | A(D3)G6(T6O18)(BO3)3X3Z |
| O | ⓘ Tourmaline | A(D3)G6(Si6O18)(BO3)3X3Z |
| O | ⓘ Quartz (var: Smoky Quartz) | SiO2 |
| O | ⓘ Beryl | Be3Al2(Si6O18) |
| O | ⓘ Cassiterite | SnO2 |
| O | ⓘ Cookeite | (Al2Li)Al2(AlSi3O10)(OH)8 |
| O | ⓘ Microcline | K(AlSi3O8) |
| O | ⓘ Staurolite | Fe22+Al9Si4O23(OH) |
| O | ⓘ Spessartine | Mn32+Al2(SiO4)3 |
| O | ⓘ Kaolinite | Al2(Si2O5)(OH)4 |
| O | ⓘ Albite | Na(AlSi3O8) |
| O | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| O | ⓘ Quartz | SiO2 |
| O | ⓘ Albite (var: Cleavelandite) | Na(AlSi3O8) |
| Na | Sodium | |
| Na | ⓘ Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| Na | ⓘ Albite | Na(AlSi3O8) |
| Na | ⓘ Albite (var: Cleavelandite) | Na(AlSi3O8) |
| Al | Aluminium | |
| Al | ⓘ Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| Al | ⓘ Beryl (var: Morganite) | Be3Al2(Si6O18) |
| Al | ⓘ Beryl (var: Aquamarine) | Be3Al2Si6O18 |
| Al | ⓘ Beryl (var: Goshenite) | Be3Al2(Si6O18) |
| Al | ⓘ Beryl | Be3Al2(Si6O18) |
| Al | ⓘ Cookeite | (Al2Li)Al2(AlSi3O10)(OH)8 |
| Al | ⓘ Microcline | K(AlSi3O8) |
| Al | ⓘ Staurolite | Fe22+Al9Si4O23(OH) |
| Al | ⓘ Spessartine | Mn32+Al2(SiO4)3 |
| Al | ⓘ Kaolinite | Al2(Si2O5)(OH)4 |
| Al | ⓘ Albite | Na(AlSi3O8) |
| Al | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Al | ⓘ Albite (var: Cleavelandite) | Na(AlSi3O8) |
| Si | Silicon | |
| Si | ⓘ Elbaite | Na(Li1.5Al1.5)Al6(Si6O18)(BO3)3(OH)3(OH) |
| Si | ⓘ Beryl (var: Morganite) | Be3Al2(Si6O18) |
| Si | ⓘ Beryl (var: Aquamarine) | Be3Al2Si6O18 |
| Si | ⓘ Beryl (var: Goshenite) | Be3Al2(Si6O18) |
| Si | ⓘ Tourmaline | A(D3)G6(Si6O18)(BO3)3X3Z |
| Si | ⓘ Quartz (var: Smoky Quartz) | SiO2 |
| Si | ⓘ Beryl | Be3Al2(Si6O18) |
| Si | ⓘ Cookeite | (Al2Li)Al2(AlSi3O10)(OH)8 |
| Si | ⓘ Microcline | K(AlSi3O8) |
| Si | ⓘ Staurolite | Fe22+Al9Si4O23(OH) |
| Si | ⓘ Spessartine | Mn32+Al2(SiO4)3 |
| Si | ⓘ Kaolinite | Al2(Si2O5)(OH)4 |
| Si | ⓘ Albite | Na(AlSi3O8) |
| Si | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Si | ⓘ Quartz | SiO2 |
| Si | ⓘ Albite (var: Cleavelandite) | Na(AlSi3O8) |
| K | Potassium | |
| K | ⓘ Microcline | K(AlSi3O8) |
| K | ⓘ Muscovite | KAl2(AlSi3O10)(OH)2 |
| Mn | Manganese | |
| Mn | ⓘ Spessartine | Mn32+Al2(SiO4)3 |
| Fe | Iron | |
| Fe | ⓘ Staurolite | Fe22+Al9Si4O23(OH) |
| Sn | Tin | |
| Sn | ⓘ Cassiterite | SnO2 |
| Ta | Tantalum | |
| Ta | ⓘ Microlite Group | A2-mTa2X6-wZ-n |
References
Sort by
Year (asc) Year (desc) Author (A-Z) Author (Z-A)Barton, William R. and Carl E. Goldsmith. (1968): New England Beryllium Investigations. U. S. Bureau of Mines: Report of Investigations 7070.
Jarnot, Bruce. (1995): The Brack Prospect: A Decomposed Lithia Gem Pegmatite in Glastonbury, Connecticut. Rocks & Minerals: 70(2): 128.
Jarnot, Bruce. (1995): Connecticut Gems & Gem Minerals. Rocks & Minerals (Connecticut Issue): 70(6): 378-382.
Weber, Marcelle H. and Earle C. Sullivan. (1995): Connecticut Mineral Locality Index. Rocks & Minerals (Connecticut Issue): 70(6): 396-409.
Other Regions, Features and Areas containing this locality
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Brack Gem prospect, East Glastonbury, Glastonbury, Hartford Co., Connecticut, USA