Timms Hill (Tim's Hill; Iolite Hill), Haddam, Middlesex County, Connecticut, USAi
| Regional Level Types | |
|---|---|
| Timms Hill (Tim's Hill; Iolite Hill) | Hill |
| Haddam | Town |
| Middlesex County | County |
| Connecticut | State |
| USA | Country |
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Latitude & Longitude (WGS84):
41° 28' 11'' North , 72° 31' 27'' West
Latitude & Longitude (decimal):
Type:
Köppen climate type:
Nearest Settlements:
| Place | Population | Distance |
|---|---|---|
| Higganum | 1,698 (2017) | 4.1km |
| East Haddam | 9,042 (2017) | 5.6km |
| Moodus | 1,413 (2017) | 7.2km |
| Chester Center | 1,558 (2017) | 9.7km |
| East Hampton | 2,691 (2017) | 11.9km |
Nearest Clubs:
Local clubs are the best way to get access to collecting localities
Local clubs are the best way to get access to collecting localities
| Club | Location | Distance |
|---|---|---|
| Lapidary and Mineral Society of Central Connecticut | Meriden, Connecticut | 25km |
| New Haven Mineral Club | New Haven, Connecticut | 38km |
| Bristol Gem & Mineral Club | Bristol, Connecticut | 42km |
A very coarse-grained vein of oligoclase and smoky quartz similar to the Haddam chrysoberyl locality was uncovered at the top of the east-facing slope on Tim’s Hill in the early 19th century, apparently by "Prof. Mather" (Shepard, 1841). A crude 1845 map of Haddam includes the words "iolite" and "tumalin" near "Tims Hill". According to Davis (1901) it was worked by Nathaniel Cook.
Lacking microcline and conformable to the surrounding gneiss, it is not a true pegmatite. It hosts cordierite (iolite) and was referred to in some old literature as “Iolite Hill”. Shepard (1837) stated that the cordierite “occurs in large massive individuals, having one very eminent cleavage. Its colors are various shades of blue and green, the former predominating...it is transparent in spots, and possessed of dichroism.” Shepard (1841) gives more details and refers to its pseudomorphing mineral (a concept not yet formalized a that time) as "pinite":
The pinite is by far the most abundant variety; good plates of iolite occurring only now and then, in limited areas of a foot or two in diameter, while the pinite is often so abundant, as mechanically to take the place of mica, in the formation of the granite.
The iolite has frequently been procured here in tabular plates, several inches across; and is remarkable for the facility with which it admits of cleavage into still thinner layers. This separation is undoubtedly promoted by the presence of exceedingly thin plates of what seems to be mica. The crystals are but seldom possessed of well defined lateral planes, in consequence of the implantation upon them of mica, albite, tourmaline, and more rarely of tabular spar. When perfect, however, they are either regular hexagonal prisms, or else this form, modified by the replacement of its lateral edges. Their color is a rich dark blue, with an occasional inclination to green; the depth of the color, as is usual in this species, is enhanced by the inspection of the plates in a direction perpendicularly to their cleavage....
The pinite variety, though generally occurring in indeterminate shaped pieces, yet nevertheless is occasionally seen in forms of the same shape and regularity as the iolite, from which, however, it differs essentially in color and hardness. The peculiar tint affected by the pinite is a pale, bluish, chloride green. Its lustre is pearly, and not particularly shining, except in a few specimens, where the color approaches silver-white. Hardness 2.5. Laminae neither flexible nor elastic. Common mica frequently pervades the mineral.
The iolite has frequently been procured here in tabular plates, several inches across; and is remarkable for the facility with which it admits of cleavage into still thinner layers. This separation is undoubtedly promoted by the presence of exceedingly thin plates of what seems to be mica. The crystals are but seldom possessed of well defined lateral planes, in consequence of the implantation upon them of mica, albite, tourmaline, and more rarely of tabular spar. When perfect, however, they are either regular hexagonal prisms, or else this form, modified by the replacement of its lateral edges. Their color is a rich dark blue, with an occasional inclination to green; the depth of the color, as is usual in this species, is enhanced by the inspection of the plates in a direction perpendicularly to their cleavage....
The pinite variety, though generally occurring in indeterminate shaped pieces, yet nevertheless is occasionally seen in forms of the same shape and regularity as the iolite, from which, however, it differs essentially in color and hardness. The peculiar tint affected by the pinite is a pale, bluish, chloride green. Its lustre is pearly, and not particularly shining, except in a few specimens, where the color approaches silver-white. Hardness 2.5. Laminae neither flexible nor elastic. Common mica frequently pervades the mineral.
Shepard (1841) noted the similarity of his "pinite" to micaceous "chlorophyllite" from New Hampshire "near J. Neal's mine in Unity". Later writers refer to the fine-grained alteration of cordierite as “fahlunite” and bright green micaceous alteration as “chlorophyllite”. Schorl crystals are also present as “short, doubly terminated black tourmalines (5 to 10 mm. in length).” (Foye (1922)). Williams (circa 1945) states that the “Oligoclase can be had in transparent clear masses.”
The lat. and long. of the primary cordierite locality on Tim's Hill is given below, but other smaller outcrops occur at the top of the slope for 250 meters or more along strike to the north and south. Much anthophyllite can be seen in these outcrops as well.
Regarding bismuthinite, Shepard (1870) reported, "large crystalline masses of bismuthine, more or less coated by bismutite, from a quarryman who had discovered them on the iolite hill...One of the specimens weighs about half a pound; and constitutes a deeply striated or channeled crystal." However, given the lack of further finds, Williams (circa 1945) suggests that the source was really the chrysoberyl locality, where it is well known, and that “the quarryman no doubt did not want to give the right locality.”
Striated magnetites are found at the oligoclase/cordierite rock. The flat-faced, octahedral magnetite crystals come from a chlorite schist at the far south end of the hill, within the power line ROW. This locality has its own page at: http://www.mindat.org/loc-263165.html
Select Mineral List Type
Standard Detailed Gallery Strunz Chemical ElementsDetailed Mineral List:
| ✪ Albite Formula: Na(AlSi3O8) Habit: anhedral but in large cleavable masses Colour: white to pale green Description: Gemmy and in large cleavable masses. |
| ✪ Albite var. Oligoclase Formula: (Na,Ca)[Al(Si,Al)Si2O8] Habit: anhedral but in large cleavable masses Colour: white to pale green Description: Gemmy and in large cleavable masses. |
| ⓘ 'Allanite Group' ? Formula: (A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH) Description: Mentioned by Foye (1922) as occurring there, but specimens are lacking. |
| ✪ Anthophyllite Formula: ◻{Mg2}{Mg5}(Si8O22)(OH)2 Habit: feathery to acicular prisms Colour: dark green to green-brown Description: In radiating sprays of acicular crystals several cm long as layers in light gneiss. |
| ⓘ 'Biotite' Formula: K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 References: |
| ⓘ Bismuthinite ? Formula: Bi2S3 Description: May be erroneous, possibly really from the chrysoberyl locality with similar mineralogy and where it is well-known. |
| ⓘ 'Chlorophyllite' Habit: coarse, micaceous pseudomorphs after cordierite Colour: green Description: Term used loosely to describe the micaceous mineral of the cordierite pseudomorphs. |
| ✪ Cordierite Formula: (Mg,Fe)2Al3(AlSi5O18) Habit: pseudohexagonal prism, subhedral blocky to massive Colour: violet, blue, pale green Description: Shows good cleavage and typically gemmy, though some of it is altered to dull gray-green "fahlunite".
"The iolite has frequently been procured here in tabular plates, several inches across; and is remarkable for the facility with which it admits of cleavage into still thinner layers. This separation is undoubtedly promoted by the presence of exceedingly thin plates of what seems to be mica. The crystals are but seldom possessed of well defined lateral planes, in consequence of the implantation upon them of mica, albite, tourmaline, and more rarely of tabular spar. When perfect, however, they are either regular hexagonal prisms, or else this form, modified by the replacement of its lateral edges. Their color is a rich dark blue, with an occasional inclination to green; the depth of the color, as is usual in this species, is enhanced by the inspection of the plates in a direction perpendicularly to their cleavage." Shepard (1841)
"Many beautiful specimens of a clear blue color have been found and cut into gems, showing dichroism by transmitted light. Specimens of this mineral seen in the different collections and museums of this country, you will invariably see labeled from Haddam. The alterations of this mineral are met with here in large quantities." (Davis, 1901). References: |
| ✪ 'Fahlunite' Formula: (Mg,Fe)Al2Si3O10 · 2H2O Habit: pseudomorphs after cordierite Colour: dull olive green Description: "The pinite [later fahlunite] variety, though generally occurring in indeterminate shaped pieces, yet nevertheless is occasionally seen in forms of the same shape and regularity as the iolite, from which, however, it differs essentially in color and hardness. The peculiar tint affected by the pinite is a pale, bluish, chloride green. Its lustre is pearly, and not particularly shining, except in a few specimens, where the color approaches silver-white. Hardness 2.5. Laminae neither flexible nor elastic.
"in rhombic prisms in great abundance at the Iolite locality, and desirable specimens are easily obtainable. Many of these specimens upon being broken show clear blue Iolite in the interior, from which mineral it, is derived as alteration." (Davis, 1901). References: |
| ⓘ Gahnite Formula: ZnAl2O4 Description: Mentioned by Foye (1922) as occurring there, but specimens are lacking. |
| ⓘ Ilmenite Formula: Fe2+TiO3 |
| ⓘ Magnetite Formula: Fe2+Fe3+2O4 Habit: striated octahedral Colour: metallic black to gray Description: Small striated crystals are found in the oligoclase-cordierite vein. References: |
| ⓘ Meta-autunite Formula: Ca(UO2)2(PO4)2 · 6H2O Description: Often coating schorl crystals (Davis, 1901). |
| ⓘ Quartz Formula: SiO2 Habit: anhedral Colour: smoky References: |
| ⓘ Quartz var. Smoky Quartz Formula: SiO2 Habit: anhedral Colour: smoky References: |
| ✪ Schorl Formula: NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) Habit: short trigonal prisms, doubly-terminated Colour: black Description: "Excellent doubly-terminated crystals of black tourmaline, 1 to 2 inches in length, and 1/2 to 1 inch in diameter are found at the Iolite locality, often covered with incrustation of autunite." (Davis, 1901). |
Gallery:
List of minerals arranged by Strunz 10th Edition classification
| Group 2 - Sulphides and Sulfosalts | |||
|---|---|---|---|
| ⓘ | Bismuthinite ? | 2.DB.05 | Bi2S3 |
| Group 4 - Oxides and Hydroxides | |||
| ⓘ | Gahnite | 4.BB.05 | ZnAl2O4 |
| ⓘ | Magnetite | 4.BB.05 | Fe2+Fe3+2O4 |
| ⓘ | Ilmenite | 4.CB.05 | Fe2+TiO3 |
| ⓘ | Quartz | 4.DA.05 | SiO2 |
| ⓘ | var. Smoky Quartz | 4.DA.05 | SiO2 |
| Group 8 - Phosphates, Arsenates and Vanadates | |||
| ⓘ | Meta-autunite | 8.EB.10 | Ca(UO2)2(PO4)2 · 6H2O |
| Group 9 - Silicates | |||
| ⓘ | Cordierite | 9.CJ.10 | (Mg,Fe)2Al3(AlSi5O18) |
| ⓘ | Schorl | 9.CK.05 | NaFe2+3Al6(Si6O18)(BO3)3(OH)3(OH) |
| ⓘ | Anthophyllite | 9.DD.05 | ◻{Mg2}{Mg5}(Si8O22)(OH)2 |
| ⓘ | Albite | 9.FA.35 | Na(AlSi3O8) |
| ⓘ | var. Oligoclase | 9.FA.35 | (Na,Ca)[Al(Si,Al)Si2O8] |
| Unclassified | |||
| ⓘ | 'Biotite' | - | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| ⓘ | 'Chlorophyllite' | - | |
| ⓘ | 'Fahlunite' | - | (Mg,Fe)Al2Si3O10 · 2H2O |
| ⓘ | 'Allanite Group' ? | - | (A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH) |
List of minerals for each chemical element
| H | Hydrogen | |
|---|---|---|
| H | ⓘ Anthophyllite | ◻{Mg2}{Mg5}(Si8O22)(OH)2 |
| H | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| H | ⓘ Fahlunite | (Mg,Fe)Al2Si3O10 · 2H2O |
| H | ⓘ Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
| H | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| H | ⓘ Allanite Group | (A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH) |
| B | Boron | |
| B | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| O | Oxygen | |
| O | ⓘ Albite | Na(AlSi3O8) |
| O | ⓘ Anthophyllite | ◻{Mg2}{Mg5}(Si8O22)(OH)2 |
| O | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| O | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| O | ⓘ Fahlunite | (Mg,Fe)Al2Si3O10 · 2H2O |
| O | ⓘ Gahnite | ZnAl2O4 |
| O | ⓘ Ilmenite | Fe2+TiO3 |
| O | ⓘ Magnetite | Fe2+Fe23+O4 |
| O | ⓘ Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
| O | ⓘ Albite var. Oligoclase | (Na,Ca)[Al(Si,Al)Si2O8] |
| O | ⓘ Quartz | SiO2 |
| O | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| O | ⓘ Quartz var. Smoky Quartz | SiO2 |
| O | ⓘ Allanite Group | (A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH) |
| F | Fluorine | |
| F | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Na | Sodium | |
| Na | ⓘ Albite | Na(AlSi3O8) |
| Na | ⓘ Albite var. Oligoclase | (Na,Ca)[Al(Si,Al)Si2O8] |
| Na | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Mg | Magnesium | |
| Mg | ⓘ Anthophyllite | ◻{Mg2}{Mg5}(Si8O22)(OH)2 |
| Mg | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Mg | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Mg | ⓘ Fahlunite | (Mg,Fe)Al2Si3O10 · 2H2O |
| Al | Aluminium | |
| Al | ⓘ Albite | Na(AlSi3O8) |
| Al | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Al | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Al | ⓘ Fahlunite | (Mg,Fe)Al2Si3O10 · 2H2O |
| Al | ⓘ Gahnite | ZnAl2O4 |
| Al | ⓘ Albite var. Oligoclase | (Na,Ca)[Al(Si,Al)Si2O8] |
| Al | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Si | Silicon | |
| Si | ⓘ Albite | Na(AlSi3O8) |
| Si | ⓘ Anthophyllite | ◻{Mg2}{Mg5}(Si8O22)(OH)2 |
| Si | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Si | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Si | ⓘ Fahlunite | (Mg,Fe)Al2Si3O10 · 2H2O |
| Si | ⓘ Albite var. Oligoclase | (Na,Ca)[Al(Si,Al)Si2O8] |
| Si | ⓘ Quartz | SiO2 |
| Si | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Si | ⓘ Quartz var. Smoky Quartz | SiO2 |
| Si | ⓘ Allanite Group | (A12+REE3+)(M13+M23+M32+)O[Si2O7][SiO4](OH) |
| P | Phosphorus | |
| P | ⓘ Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
| S | Sulfur | |
| S | ⓘ Bismuthinite | Bi2S3 |
| K | Potassium | |
| K | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Ca | Calcium | |
| Ca | ⓘ Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
| Ca | ⓘ Albite var. Oligoclase | (Na,Ca)[Al(Si,Al)Si2O8] |
| Ti | Titanium | |
| Ti | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Ti | ⓘ Ilmenite | Fe2+TiO3 |
| Fe | Iron | |
| Fe | ⓘ Biotite | K(Fe2+/Mg)2(Al/Fe3+/Mg/Ti)([Si/Al/Fe]2Si2O10)(OH/F)2 |
| Fe | ⓘ Cordierite | (Mg,Fe)2Al3(AlSi5O18) |
| Fe | ⓘ Fahlunite | (Mg,Fe)Al2Si3O10 · 2H2O |
| Fe | ⓘ Ilmenite | Fe2+TiO3 |
| Fe | ⓘ Magnetite | Fe2+Fe23+O4 |
| Fe | ⓘ Schorl | NaFe32+Al6(Si6O18)(BO3)3(OH)3(OH) |
| Zn | Zinc | |
| Zn | ⓘ Gahnite | ZnAl2O4 |
| Bi | Bismuth | |
| Bi | ⓘ Bismuthinite | Bi2S3 |
| U | Uranium | |
| U | ⓘ Meta-autunite | Ca(UO2)2(PO4)2 · 6H2O |
Other Regions, Features and Areas containing this locality
North AmericaContinent
North America PlateTectonic Plate
- Ganderia DomainDomain
- GranderiaPassive Margin
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References
Shepard, Charles Upham (1837) A Report on the Geological Survey of Connecticut. Geological Survey of Connecticut.
Foye, Wilbur G. (1922) Mineral localities in the vicinity of Middletown, Connecticut. American Mineralogist, 7 (1) 4-12
Timms Hill, Haddam, Middlesex County, Connecticut, USA