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Rockport, Essex Co., Massachusetts, USAi
Regional Level Types
Rockport- not defined -
Essex Co.County
MassachusettsState
USACountry

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Latitude & Longitude (WGS84): 42° 39' 20'' North , 70° 37' 13'' West
Latitude & Longitude (decimal): 42.65556,-70.62028
GeoHash:G#: drtf8vpys
Köppen climate type:Dfb : Warm-summer humid continental climate
Nearest Settlements:
PlacePopulationDistance
Rockport4,966 (2017)0.0km
Gloucester29,781 (2017)5.6km
Essex1,471 (2017)13.5km
Manchester-by-the-Sea5,366 (2017)14.9km
Ipswich4,222 (2017)18.2km


The town of Rockport was separated from Gloucester and incorporated in 1840. Granite was quarried here beginning in 1823. Interesting minerals occur in granite quarries and other bedrock exposures of alkaline Cape Ann granite and associated pegmatites and miarolitic cavities.

McKinstry (1921) described some of the town's mineralogical highlights: "More than fifty years ago attention was called to the unusual mineral occurrences at Rockport, on Cape Ann, by J. P. Cooke's description of danalite, a new beryllium mineral, and subsequently of cryophyllite, a new lithium mica. Besides being the type locality for these species, the Rockport quarries have afforded an interesting list of rare-earth minerals, and, perhaps most unusual of all, large tabular crystals of fayalite, normally an utter stranger to granitic rocks."

Regions containing this locality

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Standard Detailed Strunz Dana Chemical Elements

Mineral List

Mineral list contains entries from the region specified including sub-localities

29 valid minerals. 2 (TL) - type locality of valid minerals. 1 erroneous literature entry.

Rock Types Recorded

Note: this is a very new system on mindat.org and data is currently VERY limited. Please bear with us while we work towards adding this information!

Rock list contains entries from the region specified including sub-localities

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Alphabetical List Tree Diagram

Detailed Mineral List:

Actinolite
Formula: ☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Description: Reported from pegmatite in alkalic granite. Likely a sodic amphibole or aegirine.
Reference: Sears, John Henry (1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County
Albite
Formula: Na(AlSi3O8)
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
'Albite-Anorthite Series'
Reference: Dale, Thomas Nelson (1908): The Chief Commercial Granites of MA, NH, and RI (USGS Bulletin 354).
'Allanite Group'
Formula: {A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
Annite (TL)
Formula: KFe2+3(AlSi3O10)(OH)2
Type Locality:
Reference: Dana (1868), A System of Mineralogy, 5th edition; Dyar, M. Darby and Burns, Roger G. (1986): Miissbauer spectral study of ferruginous one-layer trioctahedral micas (American Mineralogist, Volume 71, pages 955-965).
'Apatite'
Astrophyllite
Formula: K2NaFe2+7Ti2Si8O28(OH)4F
Reference: Sears, J. H. (1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County, p. 241.; Toulmin, Priestley, 1957, v. 42, p.912-915.
Augite
Formula: (CaxMgyFez)(Mgy1Fez1)Si2O6
Reference: Dale, Thomas Nelson (1908): The Chief Commercial Granites of MA, NH, and RI (USGS Bulletin 354).
'Biotite'
Reference: Januzzi, R.E. and Seaman, David M. (1976) Mineral Localities Of Connecticut and Southern New York State and Pegmatite Minerals of the World.
Calcite
Formula: CaCO3
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
'Chlorite Group'
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
'Cryophyllite'
Description: A discredited mineral.
Reference: Parsons, J.: On Cryophyllite. Am. Jour. Sci. (2), xliii, 217. (1867); Sears, J. H.(1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County.
Danalite (TL)
Formula: Be3Fe2+4(SiO4)3S
Reference: Handbook of Mineralogy - Anthony, Bideaux, Bladh, Nichols; Yale Peabody Museum no. 777; Sears, J. H.(1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County.
Fayalite
Formula: Fe2+2SiO4
Reference: Palache, Charles (1950): Fayalite at Rockport, Massachusetts. (American Mineralogist 35:877)
'Fergusonite'
Reference: Yale Peabody Museum no. 161 and 1674; Januzzi, R.E. and Seaman, David M. (1976) Mineral Localities Of Connecticut and Southern New York State and Pegmatite Minerals of the World; Sears, J. H.(1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County.
Fergusonite-(Y)
Formula: YNbO4
Reference: www.handbookofmineralogy.org/pdfs/fergusonitey.pdf
Ferro-anthophyllite
Formula: ☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2
Reference: www.agu.org/cgi-bin/wais?l=V21B-01; Bozhilov, K. N. & Evans, B. W., 2001. Ferroanthophyllite in Rockport grunerite: A transmission electron microscopy study.(AmMin 86(10):1252-1260.)
Fluorite
Formula: CaF2
Fluorite var: Yttrocerite
Formula: (Ca,Y,Ce)F2+x
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
'Gadolinite' ?
Description: Unconfirmed. Collected 1920. ID based on resemblence to gadolinite from Texas, though a qualitative analysis is lacking (McKinstry, 1921: Minerals of Rockport, Mass; AmMin 6:59).
Reference: Harvard Mineralogical Museum #110632
Galena
Formula: PbS
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
Genthelvite
Formula: Be3Zn4(SiO4)3S
Reference: Dunn, P. (1976): Genthelvite and the helvine group (Mineralogical Magazine 40:627-636).
Grunerite
Formula: ☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2
Reference: Bozhilov, K. N. & Evans, B. W., 2001. Ferroanthophyllite in Rockport grunerite: A transmission electron microscopy study.(AmMin 86(10):1252-1260.); Januzzi, R.E. and Seaman, David M. (1976) Mineral Localities Of Connecticut and Southern New York State and Pegmatite Minerals of the World.
Hastingsite
Formula: {Na}{Ca2}{Fe2+4Fe3+}(Al2Si6O22)(OH)2
Description: Chemical analysis (Lyons, 1976) identified some of the Cape Ann granite amphiboles as "ferrohastingsite" (since redefined as hastingsite.)
Reference: Lyons, Paul, 1976. The Chemistry of Riebeckites of Massachusetts (MINERALOGICAL MAGAZINE 4:473-9).
Hedenbergite
Formula: CaFe2+Si2O6
Hematite
Formula: Fe2O3
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
'Hornblende'
Reference: Dale, Thomas Nelson (1908): The Chief Commercial Granites of MA, NH, and RI (USGS Bulletin 354).
Ilmenite
Formula: Fe2+TiO3
Reference: Palache, Charles (1950): Fayalite at Rockport, Massachusetts. (American Mineralogist 35:877-881).
'Limonite'
Formula: (Fe,O,OH,H2O)
Reference: Dale, Thomas Nelson (1908): The Chief Commercial Granites of MA, NH, and RI (USGS Bulletin 354).
Magnetite
Formula: Fe2+Fe3+2O4
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
Microcline
Formula: K(AlSi3O8)
Reference: No reference listed
Microcline var: Amazonite
Formula: K(AlSi3O8)
Reference: Sears, J. H.(1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County.
Minnesotaite
Formula: Fe2+3Si4O10(OH)2
Reference: Bozhilov, K. N. & B. W. Evans (2001): Ferroanthophyllite in Rockport grunerite: A transmission electron microscopy study. (American Mineralogist 86(10):1252-1260)
Molybdenite
Formula: MoS2
Reference: Januzzi, R.E. and Seaman, David M. (1976) Mineral Localities Of Connecticut and Southern New York State and Pegmatite Minerals of the World.
Muscovite
Formula: KAl2(AlSi3O10)(OH)2
Reference: No reference listed
Orthoclase
Formula: K(AlSi3O8)
Pyrite
Formula: FeS2
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
Pyrrhotite
Formula: Fe7S8
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
Quartz
Formula: SiO2
Reference: No reference listed
Quartz var: Blue Quartz
Formula: SiO2
Reference: Palache, 1950. Fayalite at Rockport, Massachusetts. AmMin 35:877-881
Quartz var: Citrine
Formula: SiO2
Reference: ; Sears, John Henry (1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County
Quartz var: Rock Crystal
Formula: SiO2
Quartz var: Smoky Quartz
Formula: SiO2
Reference: Sears, J. H.(1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County, p. 237.
'Tantalite'
Formula: (Mn,Fe)(Ta,Nb)2O6
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
Thorite
Formula: Th(SiO4)
Thorite var: Orangite
Formula: Th(SiO4)
Reference: McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts (American Mineralogist 6:56-60).
Zircon
Formula: Zr(SiO4)
Reference: No reference listed
Zircon var: Cyrtolite
Formula: Zr[(SiO4),(OH)4]
Reference: Knowlton, W. (1867). On a new mineral from Rockport, Mass. in Am. Jour. Sci., 2nd Series, vol. XLIV, no. 131, pp 224-226,
Zirconolite
Formula: CaZrTi2O7
Reference: Januzzi, R.E. and Seaman, David M. (1976) Mineral Localities Of Connecticut and Southern New York State and Pegmatite Minerals of the World.
Zirconolite var: Polymignite
Formula: (Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Reference: Januzzi, R.E. and Seaman, David M. (1976) Mineral Localities Of Connecticut and Southern New York State and Pegmatite Minerals of the World.

List of minerals arranged by Strunz 10th Edition classification

Group 2 - Sulphides and Sulfosalts
Galena2.CD.10PbS
Molybdenite2.EA.30MoS2
Pyrite2.EB.05aFeS2
Pyrrhotite2.CC.10Fe7S8
Group 3 - Halides
Fluorite3.AB.25CaF2
var: Yttrocerite3.AB.25(Ca,Y,Ce)F2+x
Group 4 - Oxides and Hydroxides
Hematite4.CB.05Fe2O3
Ilmenite4.CB.05Fe2+TiO3
Magnetite4.BB.05Fe2+Fe3+2O4
Quartz4.DA.05SiO2
var: Blue Quartz4.DA.05SiO2
var: Citrine4.DA.05SiO2
var: Rock Crystal4.DA.05SiO2
var: Smoky Quartz4.DA.05SiO2
Zirconolite4.DH.30CaZrTi2O7
var: Polymignite4.DH.30(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Group 5 - Nitrates and Carbonates
Calcite5.AB.05CaCO3
Group 7 - Sulphates, Chromates, Molybdates and Tungstates
Fergusonite-(Y)7.GA.05YNbO4
Group 9 - Silicates
Actinolite ?9.DE.10☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Albite9.FA.35Na(AlSi3O8)
Annite (TL)9.EC.20KFe2+3(AlSi3O10)(OH)2
Astrophyllite9.DC.05K2NaFe2+7Ti2Si8O28(OH)4F
Augite9.DA.15(CaxMgyFez)(Mgy1Fez1)Si2O6
Danalite (TL)9.FB.10Be3Fe2+4(SiO4)3S
Fayalite9.AC.05Fe2+2SiO4
Ferro-anthophyllite9.DD.05☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2
Genthelvite9.FB.10Be3Zn4(SiO4)3S
Grunerite9.DE.05☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2
Hastingsite9.DE.15{Na}{Ca2}{Fe2+4Fe3+}(Al2Si6O22)(OH)2
Hedenbergite9.DA.15CaFe2+Si2O6
Microcline9.FA.30K(AlSi3O8)
var: Amazonite9.FA.30K(AlSi3O8)
Minnesotaite9.EC.05Fe2+3Si4O10(OH)2
Muscovite9.EC.15KAl2(AlSi3O10)(OH)2
Orthoclase9.FA.30K(AlSi3O8)
Thorite9.AD.30Th(SiO4)
var: Orangite9.AD.30Th(SiO4)
Zircon9.AD.30Zr(SiO4)
var: Cyrtolite9.AD.30Zr[(SiO4),(OH)4]
Unclassified Minerals, Rocks, etc.
'Albite-Anorthite Series'-
'Allanite Group'-{A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
'Apatite'-
'Biotite'-
'Chlorite Group'-
'Cryophyllite'-
'Fergusonite'-
'Gadolinite' ?-
'Hornblende'-
'Limonite'-(Fe,O,OH,H2O)
'Tantalite'-(Mn,Fe)(Ta,Nb)2O6

List of minerals arranged by Dana 8th Edition classification

Group 2 - SULFIDES
AmXp, with m:p = 1:1
Galena2.8.1.1PbS
Pyrrhotite2.8.10.1Fe7S8
AmBnXp, with (m+n):p = 1:2
Molybdenite2.12.10.1MoS2
Pyrite2.12.1.1FeS2
Group 4 - SIMPLE OXIDES
A2X3
Hematite4.3.1.2Fe2O3
Ilmenite4.3.5.1Fe2+TiO3
Group 7 - MULTIPLE OXIDES
AB2X4
Magnetite7.2.2.3Fe2+Fe3+2O4
Group 8 - MULTIPLE OXIDES CONTAINING NIOBIUM,TANTALUM OR TITANIUM
ABO4
Fergusonite-(Y)8.1.1.1YNbO4
A2B2O6(O,OH,F)
Zirconolite8.2.5.5CaZrTi2O7
Group 9 - NORMAL HALIDES
AX2
Fluorite9.2.1.1CaF2
Group 14 - ANHYDROUS NORMAL CARBONATES
A(XO3)
Calcite14.1.1.1CaCO3
Group 51 - NESOSILICATES Insular SiO4 Groups Only
Insular SiO4 Groups Only with all cations in octahedral [6] coordination
Fayalite51.3.1.1Fe2+2SiO4
Insular SiO4 Groups Only with cations in >[6] coordination
Thorite51.5.2.3Th(SiO4)
Zircon51.5.2.1Zr(SiO4)
Group 65 - INOSILICATES Single-Width,Unbranched Chains,(W=1)
Single-Width Unbranched Chains, W=1 with chains P=2
Augite65.1.3a.3(CaxMgyFez)(Mgy1Fez1)Si2O6
Hedenbergite65.1.3a.2CaFe2+Si2O6
Group 69 - INOSILICATES Chains with Side Branches or Loops
Chains with Side Branches or Loops with (P=2, and N=4, 2 branches)
Astrophyllite69.1.1.1K2NaFe2+7Ti2Si8O28(OH)4F
Group 71 - PHYLLOSILICATES Sheets of Six-Membered Rings
Sheets of 6-membered rings with 2:1 layers
Annite (TL)71.2.2b.3KFe2+3(AlSi3O10)(OH)2
Minnesotaite71.2.1.5Fe2+3Si4O10(OH)2
Muscovite71.2.2a.1KAl2(AlSi3O10)(OH)2
Group 75 - TECTOSILICATES Si Tetrahedral Frameworks
Si Tetrahedral Frameworks - SiO2 with [4] coordinated Si
Quartz75.1.3.1SiO2
Group 76 - TECTOSILICATES Al-Si Framework
Al-Si Framework with Al-Si frameworks
Albite76.1.3.1Na(AlSi3O8)
Microcline76.1.1.5K(AlSi3O8)
Orthoclase76.1.1.1K(AlSi3O8)
Al-Si Framework Feldspathoids and related species
Danalite (TL)76.2.4.2Be3Fe2+4(SiO4)3S
Genthelvite76.2.4.3Be3Zn4(SiO4)3S
Unclassified Minerals, Mixtures, etc.
Actinolite ?-☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
'Albite-Anorthite Series'-
'Allanite Group'-{A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
'Apatite'-
'Biotite'-
'Chlorite Group'-
'Cryophyllite'-
'Fergusonite'-
Ferro-anthophyllite-☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2
Fluorite
var: Yttrocerite
-(Ca,Y,Ce)F2+x
'Gadolinite' ?-
Grunerite-☐{Fe2+2}{Fe2+5}(Si8O22)(OH)2
Hastingsite-{Na}{Ca2}{Fe2+4Fe3+}(Al2Si6O22)(OH)2
'Hornblende'-
'Limonite'-(Fe,O,OH,H2O)
Microcline
var: Amazonite
-K(AlSi3O8)
Quartz
var: Blue Quartz
-SiO2
var: Citrine-SiO2
var: Rock Crystal-SiO2
var: Smoky Quartz-SiO2
'Tantalite'-(Mn,Fe)(Ta,Nb)2O6
Thorite
var: Orangite
-Th(SiO4)
Zircon
var: Cyrtolite
-Zr[(SiO4),(OH)4]
Zirconolite
var: Polymignite
-(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4

List of minerals for each chemical element

HHydrogen
H AnniteKFe32+(AlSi3O10)(OH)2
H Zircon (var: Cyrtolite)Zr[(SiO4),(OH)4]
H MuscoviteKAl2(AlSi3O10)(OH)2
H Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
H Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
H AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
H Ferro-anthophyllite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
H Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
H MinnesotaiteFe32+Si4O10(OH)2
H Limonite(Fe,O,OH,H2O)
H Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
BeBeryllium
Be DanaliteBe3Fe42+(SiO4)3S
Be GenthelviteBe3Zn4(SiO4)3S
CCarbon
C CalciteCaCO3
OOxygen
O AnniteKFe32+(AlSi3O10)(OH)2
O DanaliteBe3Fe42+(SiO4)3S
O Zircon (var: Cyrtolite)Zr[(SiO4),(OH)4]
O QuartzSiO2
O MicroclineK(AlSi3O8)
O MuscoviteKAl2(AlSi3O10)(OH)2
O ZirconZr(SiO4)
O Microcline (var: Amazonite)K(AlSi3O8)
O Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
O Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
O Quartz (var: Citrine)SiO2
O Quartz (var: Rock Crystal)SiO2
O FayaliteFe22+SiO4
O Quartz (var: Smoky Quartz)SiO2
O Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
O AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
O OrthoclaseK(AlSi3O8)
O Ferro-anthophyllite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
O ThoriteTh(SiO4)
O Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
O Quartz (var: Blue Quartz)SiO2
O IlmeniteFe2+TiO3
O HedenbergiteCaFe2+Si2O6
O CalciteCaCO3
O MagnetiteFe2+Fe23+O4
O AlbiteNa(AlSi3O8)
O HematiteFe2O3
O Tantalite(Mn,Fe)(Ta,Nb)2O6
O Thorite (var: Orangite)Th(SiO4)
O GenthelviteBe3Zn4(SiO4)3S
O Fergusonite-(Y)YNbO4
O MinnesotaiteFe32+Si4O10(OH)2
O Limonite(Fe,O,OH,H2O)
O Augite(CaxMgyFez)(Mgy1Fez1)Si2O6
O ZirconoliteCaZrTi2O7
O Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
FFluorine
F FluoriteCaF2
F AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
F Fluorite (var: Yttrocerite)(Ca,Y,Ce)F2+x
NaSodium
Na AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
Na Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
Na AlbiteNa(AlSi3O8)
MgMagnesium
Mg Augite(CaxMgyFez)(Mgy1Fez1)Si2O6
Mg Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
AlAluminium
Al AnniteKFe32+(AlSi3O10)(OH)2
Al MicroclineK(AlSi3O8)
Al MuscoviteKAl2(AlSi3O10)(OH)2
Al Microcline (var: Amazonite)K(AlSi3O8)
Al OrthoclaseK(AlSi3O8)
Al Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
Al AlbiteNa(AlSi3O8)
SiSilicon
Si AnniteKFe32+(AlSi3O10)(OH)2
Si DanaliteBe3Fe42+(SiO4)3S
Si Zircon (var: Cyrtolite)Zr[(SiO4),(OH)4]
Si QuartzSiO2
Si MicroclineK(AlSi3O8)
Si MuscoviteKAl2(AlSi3O10)(OH)2
Si ZirconZr(SiO4)
Si Microcline (var: Amazonite)K(AlSi3O8)
Si Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
Si Quartz (var: Citrine)SiO2
Si Quartz (var: Rock Crystal)SiO2
Si FayaliteFe22+SiO4
Si Quartz (var: Smoky Quartz)SiO2
Si Allanite Group{A12+REE3+}{M23+M32+}(Si2O7)(SiO4)O(OH)
Si AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
Si OrthoclaseK(AlSi3O8)
Si Ferro-anthophyllite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
Si ThoriteTh(SiO4)
Si Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
Si Quartz (var: Blue Quartz)SiO2
Si HedenbergiteCaFe2+Si2O6
Si AlbiteNa(AlSi3O8)
Si Thorite (var: Orangite)Th(SiO4)
Si GenthelviteBe3Zn4(SiO4)3S
Si MinnesotaiteFe32+Si4O10(OH)2
Si Augite(CaxMgyFez)(Mgy1Fez1)Si2O6
Si Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
SSulfur
S DanaliteBe3Fe42+(SiO4)3S
S MolybdeniteMoS2
S GalenaPbS
S PyriteFeS2
S PyrrhotiteFe7S8
S GenthelviteBe3Zn4(SiO4)3S
KPotassium
K AnniteKFe32+(AlSi3O10)(OH)2
K MicroclineK(AlSi3O8)
K MuscoviteKAl2(AlSi3O10)(OH)2
K Microcline (var: Amazonite)K(AlSi3O8)
K AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
K OrthoclaseK(AlSi3O8)
CaCalcium
Ca Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Ca FluoriteCaF2
Ca Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
Ca HedenbergiteCaFe2+Si2O6
Ca CalciteCaCO3
Ca Fluorite (var: Yttrocerite)(Ca,Y,Ce)F2+x
Ca Augite(CaxMgyFez)(Mgy1Fez1)Si2O6
Ca ZirconoliteCaZrTi2O7
Ca Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
TiTitanium
Ti Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Ti AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
Ti IlmeniteFe2+TiO3
Ti ZirconoliteCaZrTi2O7
MnManganese
Mn Tantalite(Mn,Fe)(Ta,Nb)2O6
FeIron
Fe AnniteKFe32+(AlSi3O10)(OH)2
Fe DanaliteBe3Fe42+(SiO4)3S
Fe Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Fe Grunerite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
Fe FayaliteFe22+SiO4
Fe AstrophylliteK2NaFe72+Ti2Si8O28(OH)4F
Fe Ferro-anthophyllite☐{Fe22+}{Fe52+}(Si8O22)(OH)2
Fe Hastingsite{Na}{Ca2}{Fe42+Fe3+}(Al2Si6O22)(OH)2
Fe IlmeniteFe2+TiO3
Fe HedenbergiteCaFe2+Si2O6
Fe MagnetiteFe2+Fe23+O4
Fe HematiteFe2O3
Fe PyriteFeS2
Fe PyrrhotiteFe7S8
Fe Tantalite(Mn,Fe)(Ta,Nb)2O6
Fe MinnesotaiteFe32+Si4O10(OH)2
Fe Limonite(Fe,O,OH,H2O)
Fe Augite(CaxMgyFez)(Mgy1Fez1)Si2O6
Fe Actinolite☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
ZnZinc
Zn GenthelviteBe3Zn4(SiO4)3S
YYttrium
Y Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Y Fluorite (var: Yttrocerite)(Ca,Y,Ce)F2+x
Y Fergusonite-(Y)YNbO4
ZrZirconium
Zr Zircon (var: Cyrtolite)Zr[(SiO4),(OH)4]
Zr ZirconZr(SiO4)
Zr Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Zr ZirconoliteCaZrTi2O7
NbNiobium
Nb Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Nb Tantalite(Mn,Fe)(Ta,Nb)2O6
Nb Fergusonite-(Y)YNbO4
MoMolybdenum
Mo MolybdeniteMoS2
CeCerium
Ce Fluorite (var: Yttrocerite)(Ca,Y,Ce)F2+x
TaTantalum
Ta Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Ta Tantalite(Mn,Fe)(Ta,Nb)2O6
PbLead
Pb GalenaPbS
ThThorium
Th Zirconolite (var: Polymignite)(Ca,Fe,Y,Th)(Nb,Ti,Ta,Zr)O4
Th ThoriteTh(SiO4)
Th Thorite (var: Orangite)Th(SiO4)

Regional Geology

This geological map and associated information on rock units at or nearby to the coordinates given for this locality is based on relatively small scale geological maps provided by various national Geological Surveys. This does not necessarily represent the complete geology at this locality but it gives a background for the region in which it is found.

Click on geological units on the map for more information. Click here to view full-screen map on Macrostrat.org

Paleozoic
251.902 - 541 Ma



ID: 3191988
Paleozoic intrusive rocks

Age: Phanerozoic (251.902 - 541 Ma)

Lithology: Intrusive igneous rocks

Reference: Chorlton, L.B. Generalized geology of the world: bedrock domains and major faults in GIS format: a small-scale world geology map with an extended geological attribute database. doi: 10.4095/223767. Geological Survey of Canada, Open File 5529. [154]

Wenlock - Late Ordovician
427.4 - 458.4 Ma



ID: 2742559
Cape Ann Complex

Age: Paleozoic (427.4 - 458.4 Ma)

Stratigraphic Name: Cape Ann Complex

Description: Alkalic granite to quartz syenite containing ferro-hornblende. Intrudes Zdigb. Most of Cape Ann Complex forms Cape Ann peninsula of northeastern MA. Consists of alkalic granite to quartz syenite (its main phase), Beverly Syenite, and Squam Granite, all of which form a pluton covering 385 sq km. Intrudes Late Proterozoic greenschist, diorite, and gabbro that earlier workers assigned to Marlboro Formation, Salem Gabbro-Diorite, or Middlesex Fells Volcanic Complex. Dennen (1975) considered masses of diorite and gabbro within and adjacent to Cape Ann Complex to be cogenetic with it and equivalent in age to Nahant Gabbro and gabbro at Salem Neck. Authors recommend that usage of term Salem Gabbro-Diorite be restricted to these masses of diorite and gabbro in and around Cape Ann pluton that are younger than Dedham Granite and cogenetic with Cape Ann Complex. Gabbro at Salem Neck is probably representative. Radiometric ages straddle Late Ordovician-Early Silurian boundary. Age is based on Rb-Sr whole rock isochron of 426 +/-6 Ma (Zartman and Marvin, 1971) and U-Pb zircon date of 450 +/-25 Ma (Zartman, 1977) (Wones and Goldsmith, 1991).

Comments: Part of Milford-Dedham Zone (Tertiary and Older Rocks). Secondary unit description per MA007. Original map source: Unpublished Digital Geologic Map of Massachusetts received from Rudi Hon of Boston College in 1998; based on the 1983 USGS paper version (MA002).

Lithology: Major:{alkali granite,quartz syenite}

Reference: Horton, J.D., C.A. San Juan, and D.B. Stoeser. The State Geologic Map Compilation (SGMC) geodatabase of the conterminous United States. doi: 10.3133/ds1052. U.S. Geological Survey Data Series 1052. [133]

Ordovician
443.8 - 485.4 Ma



ID: 2702883
Cape Ann Granite, alkali-feldspar quartz syenite

Age: Ordovician (443.8 - 485.4 Ma)

Stratigraphic Name: Cape Ann Granite

Description: Modal quartz content 5-15 percent (equivalent to nordmakite of Warren and McKinstry, 1924)

Comments: The principal rock of the map area is the Cape Ann Granite, an unfoliated, medium- to coarse-grained, leucocratic rock ranging in composition from quartzose alkali-feldspar granite, through alkali-feldspar quartz syenite, to alkali-feldspar syenite. Its texture is generally uneven, subhedral to subporphyritic, and locally cumulus. Crystals range from 0.5 to 1 cm (0.2 to 0.4 in.) long in the quartz-bearing rocks and are less uniform in the syenitic rocks. Most of the syenite is texturally equivalent to the granite, but the syenite commonly contains small, irregular pegmatitic patches that lack well-defined boundaries. The range (and median) of the principal minerals are: potassium feldspar, 53-85 (63) percent; plagioclase (An6-12), 0-22.5 (2.8) percent; quartz, 0-41 (24) percent; ferrohornblende, 0.1-17 (4.5) percent; biotite, 0-3.2 (0.8) percent; and opaque minerals, 0.2-7.5 (1.0) percent. Minor quantities of augite are in approximately one-quarter of the specimens. Accessory minerals include magnetite, ilmenite, zircon, apatite, and, very rarely, fluorite, pyrite or molybdenite. Carlsbad-twinned microcline microperthite is the dominant feldspar; less than 25 percent of the feldspar is homogeneous microcline. Plagioclase (albite or oligoclase) is present in only minor quantities. Quartz is clear, grayish, pinkish, or faintly smoky, shows weak strain shadows, and contains oriented sheets of dust-like inclusions and vesicles. Potassium feldspar and quartz occur as large single crystals and as clusters of subhedral to euhedral feldspar and anhedral quartz partly to completely surrounded by finer grained quartz and feldspar. The mafic minerals are variable in amount and appearance and occur as ragged clots, wisps, single subhedral crystals, and zoned reaction aggregates. Augite is colorless to pale green, typically occurring as a core that is partly or completely surrounded by pale-green amphibole, darker green sodium-iron amphibole, and reddish-brown biotite; magnetite granules are scattered throughout the aggregate. Sodium-iron amphibole and biotite occur as both isolated crystals and clots of both minerals. The mapped lithotypes of the Cape Ann Granite were determined by modal quartz content, because the amount of quartz in these subunits is consistent and varies smoothly in areas generally measurable in square kilometers (miles). Arbitrary divisions of 5, 15, and 25 volume percent of quartz were determined by point counts on outcrops. These lithotypes form irregular northeast-bending bands. Neither stratigraphic succession nor dips of these lithotypes is known, but field relations suggest the superposition of quartz-rich on quartz-poor types. The lithotypes probably originated by differential crystal settling, but may have had their origin in convective motions of the magma. Weathering causes sequential color changes in these felsic rocks from dark green to green gray or gray, then to brown, tan, and finally to white on exposed surfaces. The weathered surface is black-brown and grus is common under vegetation. Joints are commonly bordered by a brown zone a few centimeters (inches) thick. Xenoliths, which are generally small and well digested, but locally may retain their preincorporation character, are scattered throughout the intrusion. They include blocks of a fine-grained granite, probably the Squam Granite; Salem Gabbro-diorite and other fine-grained, commonly porphyritic mafic rocks; and siliceous metasedimentary rocks. Many of these latter were originally finely laminated (0.1 to 5 mm (0.004-0.2 in.)), but have been transformed by thermal metamorphism into thin-banded quartz-biotite rocks containing feldspars and hornblende. A few of these metasedimentary xenoliths contain muscovite, pyroxene, and garnet; one sample contains sillimanite.

Reference: Dennen, W.H. Bedrock geologic map of the Gloucester and Rockport quadrangles, Massachusetts. U.S. Geological Survey Miscellaneous Investigations Series Map I-2285. Digital Conversion 2007. [130]

Data and map coding provided by Macrostrat.org, used under Creative Commons Attribution 4.0 License

References

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Year (asc) Year (desc) Author (A-Z) Author (Z-A)
Cooke, Josiah P., Jr. (1866): On Danalite, a new Mineral Species from the Granite of Rockport, Massachusetts, American Journal of Science and Arts: 47: 73-78.
Cooke, Josiah P., Jr. (1867): On Cryophyllite, American Journal of Science and Arts: 48: 217.
Knowlton, W. J. (1867). On a new mineral from Rockport, Massachusetts [Cyrtolite], American Journal of Science and Arts, 2nd Series, 44: 224-226.
Shaler, N. S. (1888): The Geology of Cape Ann, Massachusetts, USGS Ninth Annual Report.
Merrill, George P. (1889): The Collection of Building and Ornamental Stones in the U.S. National Museum, p. 287.
Warren, Charles H. (1903) Anthophyllite [= Ferro-anthophyllite] and Fayalite from Rockport, Massachusetts, American Journal of Science, 4th series: 16: 337.
Sears, John Henry (1905): The Physical Geography, Geology, Mineralogy and Paleontology of Essex County.
McKinstry, H. E. (1921): The Minerals of Rockport, Massachusetts, American Mineralogist: 6: 56-60.
Palache, Charles (1950): Fayalite at Rockport, Massachusetts, American Mineralogist: 35: 877-881.
Dunn, P. (1976): Genthelvite and the helvine group, Mineralogical Magazine: 40: 627-636.
Lyons, Paul (1976): The Chemistry of Riebeckites of Massachusetts, Mineralogical Magazine: 4: 473-479.
Bozhilov, K. N. & B. W. Evans (2001): Ferroanthophyllite in Rockport grunerite: A transmission electron microscopy study, American Mineralogist: 86(10): 1252-1260.

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