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Baltimore Co., Maryland, USAi
Regional Level Types
Baltimore Co.County
MarylandState
USACountry

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Key
01126560014946398014000.jpg
Former McMahon Quarry - now filled with water

McMahon Quarry, Bare Hills, Baltimore Co., Maryland, USA
Locality type:
Largest Settlements:
PlacePopulation
Dundalk63,597 (2011)
Towson55,197 (2011)
Catonsville41,567 (2011)
Essex39,262 (2011)
Woodlawn37,879 (2011)
Randallstown32,430 (2011)
Other Languages:
French:
comté de Baltimore, Maryland, États-Unis
German:
Baltimore County, Maryland, Vereinigte Staaten
Italian:
contea di Baltimora, Maryland, Stati Uniti d'America
Russian:
Балтимор, Мэриленд, Соединённые Штаты Америки
Simplified Chinese:
巴爾的摩縣, 马里兰州, 美国
Spanish:
Condado de Baltimore, Maryland, Estados Unidos
Albanian:
Baltimore County, Maryland, Shtetet e Bashkuara të Amerikës
Arabic:
مقاطعة بالتيمور, ماريلند, الولايات المتحدة
Armenian:
Բալթիմոր շրջան, Մերիլենդ, Ամերիկայի Միացյալ Նահանգներ
Basque:
Baltimore konderria , Maryland
Bavarian:
Baltimore County, Maryland, Vaoanigte Stootn
Belarusian:
Балтымар, Мэрыленд, Злучаныя Штаты Амерыкі
Bengali:
বাল্টিমোর কাউন্টি, মেরিল্যান্ড, মার্কিন যুক্তরাষ্ট্র
Bishnupriya Manipuri:
বাল্টিমোর কাউন্টি, মেরিল্যান্ড, তিলপারাষ্ট্র
Bulgarian:
Балтимор, Мериленд, Съединени американски щати
Catalan:
Comtat de Baltimore, Maryland, Estats Units d’Amèrica
Cebuano:
Baltimore County, Maryland
Cornish:
Konteth Baltimore, Tir Maria, Statys Unys
Danish:
Baltimore County, Maryland, USA
Dutch:
Baltimore County, Maryland, Verenigde Staten
Esperanto:
Kantono Baltimoro, Marilando
Estonian:
Baltimore'i maakond, Maryland, Ameerika Ühendriigid
Farsi/Persian:
شهرستان بالتیمور، مریلند, مریلند, ایالات متحده آمریکا
Georgian:
ბალტიმორის ოლქი, მერილენდი, ამერიკის შეერთებული შტატები
Greek:
Κομητεία Βαλτιμόρης, Μέριλαντ, Ηνωμένες Πολιτείες Αμερικής
Hebrew:
מחוז בולטימור, מרילנד, ארצות הברית
Hungarian:
Baltimore megye, Maryland, Amerikai Egyesült Államok
Indonesian:
Baltimore County, Maryland, Amerika Serikat
Japanese:
ボルチモア郡, メリーランド州, アメリカ合衆国
Latvian:
Baltimoras grāfiste, Mērilenda, Amerikas Savienotās Valstis
Low Saxon/Low German:
Baltimore County, Maryland, USA
Min Dong Chinese:
Baltimore Gông, Maryland
Minnan / Hokkien-Taiwanese:
Baltimore Kūn
Norwegian:
Baltimore County, Maryland, USA
Polish:
Hrabstwo Baltimore, Maryland, Stany Zjednoczone
Portuguese:
Condado de Baltimore, Maryland, Estados Unidos
Romanian:
Comitatul Baltimore, Maryland, Statele Unite ale Americii
Sardinian:
contea de Baltimora, Maryland, Istados Unidos de Amèrica
Scottish Gaelic:
Baltimore County, Maryland, Na Stàitean Aonaichte
Serbian:
Округ Балтимор, Мериленд, Сједињене Америчке Државе
Serbo-Croatian:
Baltimore County, Maryland, Sjedinjene Američke Države
Slovenian:
okrožje Baltimor, Maryland, Združene države Amerike
Swedish:
Baltimore County, Maryland, USA
Tagalog:
Baltimore, Maryland, Estados Unidos
Traditional Chinese:
巴爾的摩縣, 馬利蘭州, 美國
Turkish:
Baltimore County, Maryland, Amerika Birleşik Devletleri
Ukrainian:
Балтимор, Меріленд, Сполучені Штати Америки
Urdu:
بالٹیمور کاؤنٹی، میری لینڈ, میری لینڈ, ریاستہائے متحدہ امریکا
Waray:
Condado han Baltimore, Maryland, Estados Unidos
Western Punjabi:
بالٹیمور کاؤنٹی, میری لینڈ, امریکہ


Most of Baltimore County is underlain by the complex rocks of the Piedmont Province. These are diverse igneous and metamorphic rocks that have been folded, faulted and intruded by magma multiple times during Paleozoic mountain building episodes. The oldest rock is the Baltimore Gneiss, a Precambrian sequence of highly metamorphosed volcanic and sedimentary rocks. Overlying these are Cambrian sediments that were metamorphosed into schist, quartzite and marble. A large gabbroic pluton, he Baltimore Gabbro Complex was intruded and later metamorphosed. Plate movements also incorporated chunks of ultramafic oceanic crust into the sequence. These are metamorphosed into a string of serpentinites. The most notable of these underlie the Bare Hills, where these rocks produce distinct soil and vegetation patterns. A number of granitic rocks also intruded during the various mountain building episodes. Along the east side of the county lies a cover of Cretaceous sediments from the Coastal Plain Province. Oxidized siderite nodules from the Cretaceous rocks were worked in many localities for iron ore dating back to pre-Revolutionary War time.

Most of the listed minerals are from mines and quarries in the Piedmont Province. The gabbro, gneiss and granite have long provided crushed and building stone. The ultramafic rocks were worked not only for crushed stone but also for chromite and asbestos. The marble, worked for crushed stone and agricultural lime. provides excellent collecting where exposed in quarries. A number of small iron mines, some dating back to pre-Revolutionary War times. Urbanization has covered or obscured many of the deposits. However considering the diversity of the geology, any new excavation or quarry is worth examining for mineral specimens.

Select Mineral List Type

Standard Detailed Strunz Dana Chemical Elements

Commodity List

This is a list of exploitable or exploited mineral commodities recorded from this region.


Mineral List

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

78 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

Select Rock List Type

Alphabetical List Tree Diagram

Detailed Mineral List:

Actinolite
Formula: ☐{Ca2}{Mg4.5-2.5Fe0.5-2.5}(Si8O22)(OH)2
Albite
Formula: Na(AlSi3O8)
Albite var: Oligoclase
Formula: (Na,Ca)[Al(Si,Al)Si2O8]
Reference: USGS Bull. 426
'Albite-Anorthite Series'
Reference: Ostrander, C. W. & W. E. Price (1940) Minerals of Maryland: Natural History Society of Maryland , 92 p.
'Allanite Group'
Formula: {A12+REE3+}{M3+2M32+}(Si2O7)(SiO4)O(OH)
Almandine
Formula: Fe2+3Al2(SiO4)3
Reference: Rocks & Min.: 21:144-145; Ostrander & Price (1940), Minerals of Maryland: 27.
'Amphibole Supergroup'
Formula: AX2Z5((Si,Al,Ti)8O22)(OH,F,Cl,O)2
Reference: Bernstein, L. (1976) Minerals of Washington D.C. and vicinity. U.S. Geological Survey Open-File Report 76-849, 183 pages.
Analcime
Formula: Na(AlSi2O6) · H2O
Reference: Ostrander, C. W. & W. E. Price (1940) Minerals of Maryland: Natural History Society of Maryland , 92 p.
Anthophyllite
Formula: ☐{Mg2}{Mg5}(Si8O22)(OH)2
Antigorite
Formula: Mg3(Si2O5)(OH)4
Antigorite var: Williamsite
Formula: Mg3(Si2O5)(OH)4
Reference: Ostrander, C. W. & W. E. Price (1940) Minerals of Maryland: Natural History Society of Maryland, 27p.
'Apatite'
Formula: Ca5(PO4)3(Cl/F/OH)
Aragonite
Formula: CaCO3
'Asbestos'
Reference: Rocks & Min.: 21:274-275.
'Asbestos var: Mountain Leather'
Reference: Rocks & Min.: 21:274-275.
Augite
Formula: (CaxMgyFez)(Mgy1Fez1)Si2O6
Reference: Ostrander, C. W. & W. E. Price (1940) Minerals of Maryland: Natural History Society of Maryland , 92 p.
Azurite
Formula: Cu3(CO3)2(OH)2
Reference: Rocks & Min.: 21:144-145; Ostrander & Price (1940), Minerals of Maryland: 27.
Baryte
Formula: BaSO4
Reference: Rocks & Min.: 21:274-275.
Beryl
Formula: Be3Al2(Si6O18)
Reference: MacFall, 1951. Gem Hunter's Guide, 1st ed.
Beryl var: Aquamarine
Formula: Be3Al2Si6O18
Reference: MacFall, 1951. Gem Hunter's Guide, 1st ed.
'Biotite'
Formula: K(Fe2+/Mg)2(Al/Fe3+/Mg)([Si/Al]Si2O10)(OH/F)2
Localities: Reported from at least 6 localities in this region.
Bornite
Formula: Cu5FeS4
Reference: Rocks & Min.: 21:144-145; Ostrander & Price (1940), Minerals of Maryland: 27.
Brucite
Formula: Mg(OH)2
Calcite
Formula: CaCO3
Localities: Reported from at least 17 localities in this region.
Calcite var: Iceland Spar
Formula: CaCO3
Reference: Minerals of Maryland (1940) Ostrander & Price, JR.
Carrollite
Formula: Cu(Co,Ni)2S4
Reference: U.S. Geological Survey, 2005, Mineral Resources Data System: U.S. Geological Survey, Reston, Virginia.
Chalcanthite
Formula: CuSO4 · 5H2O
Reference: Rocks & Min.: 21:144-145; Ostrander & Price (1940), Minerals of Maryland: 27.
Chalcocite
Formula: Cu2S
Reference: Rocks & Min.: 21:144-145; Ostrander & Price (1940), Minerals of Maryland: 27.
Chalcopyrite
Formula: CuFeS2
'Chlorite Group'
Localities: Reported from at least 13 localities in this region.
Chromite
Formula: Fe2+Cr3+2O4
Localities: Reported from at least 14 localities in this region.
Chrysocolla
Formula: Cu2-xAlx(H2-xSi2O5)(OH)4 · nH2O
Reference: Rocks & Min.: 21:144-145; Ostrander & Price (1940), Minerals of Maryland: 27.
Chrysotile
Formula: Mg3(Si2O5)(OH)4
'Clays'
Clinochlore
Formula: Mg5Al(AlSi3O10)(OH)8
Localities: Reported from at least 7 localities in this region.
Clinochlore var: Chromian Clinochlore
Formula: Mg5(Al,Cr)2Si3O10(OH)8
Clinozoisite
Formula: {Ca2}{Al3}(Si2O7)(SiO4)O(OH)
Reference: Bernstein, L.R. (1976) Minerals of Washington D.C. and vicinity. U.S. Geological Survey Open-File Report 76-849, 183 pages. Bernstein, L.R. (1980) Minerals of the Washington D. C. area: Maryland Geological Survey Educational Series 5, 148 pages.
Covellite
Formula: CuS
Reference: Rocks & Min.: 21:144-145; Ostrander & Price (1940), Minerals of Maryland: