Franklin Terms and Definitions

Mineral collectors who specialize in Franklin and Sterling Hill have their own unique vocabulary, from jargon, to historical references, and sometimes outdated terms. Some terms relate to specific minerals or mineral characteristics, some to the local geology, and some to locations in and around the "Franklin mining district."

Franklin Mineral Terms
Geological Terms
Location Terms

Franklin Mineral Terms
Black oreThis ore contains "black" willemite which is colored by microscopic franklinite inclusions; it is common at Sterling Hill, but uncommon at Franklin. 1001
Brown oreThis ore contains willemite colored brown from franklinite inclusions. 1025
Buckshot-oreA term used for distinctly granular franklinite-bearing ore. Local mythology is that the hard iron-oxide franklinite crystal grains that weathered out of the ore were used to reload shotgun shells. 1009
CalcozinciteIs a material comprised of admixed yellow and red zincite and compact calcite in various proportions, but the resulting color is more or less orange. Numerous embedded fibers of tremolite asbestos and/or sussexite give the whole mass a columnar fibrous appearance. Frequently found as a material lining slickensides fractures. 1028
CaswelliteA local name for grossular. 1054
ChlorophaneIs a varietal name of fluorite found at both Franklin and Sterling Hill Mine, which fluoresces greenish-blue or teal green under both short wave and long wave UV light. It also phosphoresces blue under both wavelengths. Chlorophane is thermoluminescent, and will emit these colors if heated. This fluorite is usually brown to sherry-red in daylight, but will fade to a dull brown and eventually to white / clear daylight color on exposure to sunlight or UV light. Heating will destroy the luminescent response, and light exposure will fade the fluorescent response and often change it to the more usual blue fluorite luminescence. 1029
Christmas Tree RockA local nickname for rock with a matrix of aegirine-augite, and a poikiloblastic texture, an allusion to the red-and-green color combination under SW ultraviolet light, and to the nearly spherical form of some of the fluorescent grains, reminiscent of balls on a Christmas tree. 1087
Epidote-(Pb)Was the approved name for Hancockite between 2006 and 2015. In July 2015, the IMA approved a proposal by Olav Revheim and Vandall King to revert the approved name to hancockite.
FeldsparFeldspars are a group of rock-forming tectosilicate minerals distinguished by the presence of alumina and silica (SiO2) in their chemistry. Microcline is a very common feldspar mineral at Franklin. 1083
FerrobustamiteIs the iron analogue of bustamite. It may also contain divalent Mn replacing Fe.  Lathes of white to pink ferrobustamite are sometimes found in specimens of "3rd Find" wollastonite from Franklin, and fluoresce a deep red in SW UV. 1037
Franklin MarbleA band of white marble, extending from south of Sparta, New Jersey, northerly into Orange County, New York. 1021
HyalophaneIs a barium potassium aluminum silicate mineral of the feldspar group. In Franklin it occurs in anhedral crystals and granular aggregates with substantial variation in grain size. It has not been reported to be found at Sterling Hill. Hyalophane is white to pale brown with a vitreous luster varying to somewhat pearly. Some specimens fluoresce a deep red under shortwave UV light. Hyalophane was once on the Franklin Mineral Species List, but was removed in mid-2000’s, after being discredited by the IMA using the 50/50 Rule. (Orthoclase feldspar K(AlSi 3O 8) and celsian Ba(Al 2Si 2O 8) form a solid solution series, which used to include hyalophane as an intermediate member containing both potassium and barium ions.) 1033
JeffersoniteIs a zincian manganoan variety of augite, a clinopyroxene. It is found in large crystals of simple habit, some more than 12 inches long and many doubly terminated. It occurs also in granular and platy masses. The color is dark olive-green to brown and on weathered surfaces is gray to chocolate-brown and black. 1030
LeucaugiteAn outdated synonym for diopside, in use through at least the late 1950s. See also zinc schefferite. 1035
Maggot oreHemimorphite crystal clusters that look like fly larva (maggots). example of maggot ore1004
Peacock OreA description used for iridescent franklinite. of Peacock Ore1084
Polka Dot RockA local nickname for rock with a matrix of aegirine-augite, and a poikiloblastic texture. It is also known as “Christmas tree rock,” in allusion to the red-and-green color combination under SW ultraviolet light, and to the nearly spherical form of some of the fluorescent grains, reminiscent of balls on a Christmas tree. 1086
Red oreThis ore contains pinkish-tan to dark reddish-brown willemite that is colored by franklinite inclusions. 1023
ScapoliteScapolites are a group of rock-forming silicate minerals comprised of either calcium or sodium, with aluminum silicate and either chlorine, carbonate, or sulfate. They occur as alteration minerals of feldspar, and can appear in wide variety of forms, anywhere from a stocky opaque crystal habit to translucent gemmy crystals. Meionite and marialite are end members of this solid solution series. 1082
Slick 'n slideIs a local nickname for a slickenside 1079
Third FindA Franklin wollastonite occurrence, it occurs in orange-fluorescing elongated grains, or in aggregates of grains, in a matrix of red-fluorescing calcite that also includes smaller grains of cream-fluorescing barite and, rarely, green-fluorescing willemite. A nonfluorescent unidentified amphibole, often as complete crystals, is always present. A locality and date for this occurrence, as well as a description, are given by Baum (1972). What we now call Third-Find wollastonite was found "in the hanging wall at the contact of the ore with the marble to the East, as in the 290 North top slice on the 1050 level, found in 1947”. example of Third Find wollastonite1031
Zinc SchefferiteA local area name for a variety of diopside containing small amounts of zinc. It is light brown in color. At Franklin it often has a platey habit. example of zinc schefferite1014

Geological Terms
50/50 RuleSome minerals are part of a "solid-solution series," with chemical composition and crystal structure that varies from one pure "end-member," through possible intermediate compositions, to another end-member. For example pure scheelite is calcium tungstate, CaWO4, and pure powellite is calcium molybdate, CaMoO4. There could be intermediate minerals with a mix of tungsten and molybdenum, but for simplicity, we say that if the mineral contains more tungsten ions than molybdenum ions – the mineral is termed scheelite. If instead there are more molybdenum than tungsten ions, it is called powellite, with no "50/50" minerals in the middle. 1036
AcicularCrystals which appear as sharp, slender needles either individually or in a group. 1041
AdamantineA mineral having a luster of the highest degree, similar to that of a diamond. 1040
AlterationThe chemical or physical changes in a mineral, through natural causes, resulting in the formation of a new mineral which replaces the old in whole or in part. An example would be mica replaced by grossular, locally called caswellite. replaced by grossular.1043
AmorphousA non-crystalline mineral having no clearly defined form nor shape. 1042
AmphiboleIs a group of closely related, generally dark colored rock forming silicate minerals. 1019
AssociationThe recurring presence of a mineral in the same combination with other minerals. It is an important aid in the visual identification of a mineral. e.g. Hardystonite is frequently associated with clinohedrite. Norbergite is never found in association with zincite. 1044
AugenFrom German "eyes", are lenticular eye-shaped mineral grains or mineral aggregates visible in some foliated metamorphic rocks. In a cross section they have the shape of an eye. 1038
Basal CleavageThe breakage of a mineral in only one direction, leaving a smooth flat surface where it was broken off.     1045
BotryoidalA texture or mineral habit where the mineral has a globular external form resembling a bunch of grapes. mineral example1000
BoxworkIs a mineral-aggregate structure having plates or septa that are often coated with crystals and that intersect at various angles and enclose angular spaces. example of boxwork1032
BrittleA mineral that shatters easily. It is not to be confused with the hardness of the mineral. e.g. Quartz is brittle yet it has a Mohs hardness of 7. 1046
Calc-silicateA term used to describe rock produced by metasomatic alteration of existing rocks, producing calcium silicate minerals such as diopside and wollastonite. Skarns or tactites are calcium-bearing calc–silicate rocks. 1010
CamptoniteA dark-coloured, medium-grained igneous rock, a common form of basalt, also called a lamprophyre, which characteristically forms dykes. Dikes of it cut through the limestone at Franklin.  1047
CleavageThe natural tendency of some minerals to break in certain and definite directions and where the resulting pieces have smooth, flat surfaces. It is to be distinguished from fracture. of cleavage.1048
ConchoidalDescribes the way that brittle materials break or fracture when they do not follow any natural planes of separation. In a mineral the result is a concave surface somewhat like the interior of a seashell. In a sub-conchoidal fracture the concavity is not so well defined. 1049
ConcretionaryA concretion is a hard, compact mass of material formed by the precipitation of mineral cement within the spaces between various minerals, and is found in sedimentary rock or soil. 1050
DikeIs a sheet of rock that formed in a fracture in a pre-existing rock body. They can be either magmatic or sedimentary in origin. Magmatic dikes form when magma intrudes into a crack then crystallizes as a sheet intrusion, either cutting across layers of rock or through an unlayered mass of rock. Clastic dikes are formed when sediment fills a pre-existing crack. 1026
DruzyAlso drusy. A coating of fine crystals on a rock fracture surface, vein, or within a vug or geode.  1052
ExsolutionIs a process by which an initially homogeneous solid solution separates into at least two different crystalline minerals without the addition or removal of any materials. 1017
FoliatedRefers to repetitive layering in metamorphic rocks that results from segregation of different minerals into roughly parallel layers. Each layer may be as thin as a sheet of paper, or over a meter in thickness. 1015
FractureAny irregular breakage in a rock or mineral. It is thus distinguished from cleavage where the breakage occurs along defined planes. 1053
GangueIs commercially worthless rock in which valuable minerals and metals occur in an ore deposit. At Franklin and Sterling Hill, a common example would be calcite. 1055
GranularA rock composed of mineral grains of similar size. Much of the green willemite / franklinite ore from Franklin is granular. 1056
HardnessThe relative resistance of mineral to being scratched by another substance. Measured by the Mohs hardness scale. 1057
HemimorphicA doubly-terminated mineral crystal having different crystal forms at each end of an axis. Named after hemimorphite, a common mineral at Sterling Hill. 1058
HomogeneousRefers to the uniformity of composition throughout a rock, texture. For sedimentary rocks, it is the size, shape, and arrangement of the grains. For igneous and metamorphic rocks, texture of a rock or crystals. 1018
IgneousSolid rock formed from molten and fluid material called magma. 1059
IMAThe International Mineralogical Association (IMA) is the world’s largest organization promoting mineralogy. It was founded in 1958 and has 38 national mineralogical societies or groups as members. The Association supports the activities of Commissions and Working Groups involved on certain aspects of mineralogical practice and facilitates interaction among mineralogists by sponsoring and organizing meetings. The IMA Commission on New Minerals, Nomenclature and Classification approves and publishes a list of names and details of new minerals. 1034
IridescentA mineral displaying reflected light, the colors of the rainbow. An example is the "peacock ore" patina of franklinite. 1060
JointsFractures in rock along which little or no offset has taken place parallel to the plane of the fracture. 1088
LamellaePlural for lamella, is used to refer to collections of fine sheets of material held adjacent to one another. 1016
LusterThe appearance of the mineral, in reflected light, which is different from its inherent color. Examples include metallic, glassy, adamantine, pearly, or vitreous. 1061
MalleableThe capability of a metal of being beaten into thin sheets without breaking. Malleable copper masses were found at Franklin. 1062
MatrixIs the finer-grained mass of material in which larger mineral grains, crystals, or clasts are embedded. Also called groundmass. 1063
MetamorphicAny rock that has been changed from its original chemical composition or physical appearance by high temperature or great pressure. e.g. marble is a metamorphosed limestone (physical change). 1064
Metasomatic alterationThe chemical alteration of a rock by hydrothermal and other fluids. It is the replacement of one rock by another of different mineralogical and chemical composition. Some of the minerals which compose the rocks are dissolved, and new mineral formations are deposited in their place.  1011
MicaceousA mineral of foliated or lamellar structure which can be split into thin sheets. e.g. phlogopite or biotite. 1068
MOHS Hardness ScaleThe relative resistance of a mineral to being scratched by another substance will determine its hardness and thus aid in identification.
1   Talc
2   Gypsum
3   Calcite
4   Fluorite
5   Apatite
6   Orthoclase
7   Quartz
8   Topaz
9   Corundum
10  Diamond
MylonitizationIs the deformation of a rock by extreme microbrecciation, due to mechanical forces applied in a definite direction, without noteworthy chemical changes to granulated minerals. Characteristically the mylonites produced in this manner have a banded, or streaked appearance, and augen and lenses of the parent rock in a granulated matrix. 1039
PegmatiteIs a coarsely crystalline, high silica igneous rocks such as granite, seen in abundance at Franklin. Often composed of microcline or other feldspars, quartz, mica, and rarer minerals such as allanite, thorite and zircon. 1066
PinacoidalA mineral that breaks along only one cleavage plane, showing two parallel faces, e.g. mica. 1067
Poikiloblastic TextureIs a term that refers to rounded grains of one or more minerals embedded in much larger grains of another mineral. 1085
PseudomorphIs a mineral that has been chemically altered in some way and is a new mineral which can have a new crystalline structure, but it still retains the shape of the original mineral. These changes occur when the mineral is reduced, oxidized, elements added, or when elements are completely replaced. 1020
RadiatingA crystal spray diverging from a common center. e.g. some white willemite. of radiating willemite1069
ResinousA mineral whose surface luster closely resembles the congealed sap of a tree. e.g. some types of sphalerite. 1070
SedimentaryThe weathered or decomposed materials of an older rock mass deposited elsewhere by wind or water and then formed into new rock. e.g. sandstone, shale. Speleothemes found inside the Sterling Hill Mine are post-mining sedimentary deposits. 1071
SkarnAre calcium-bearing calc–silicate rocks most often formed at the contact zone between intrusions of granitic magma bodies and carbonate sedimentary rocks such as limestone and dolostone. Hot fluids derived from the granitic magma are rich in silica, iron, aluminum, and magnesium. These fluids mix in the contact zone, dissolve calcium-rich carbonate rocks, and convert the host carbonate rock to skarn deposits in a metamorphic process called metasomatism. 1022
SlickensidesRefers to a naturally polished fault surface due to friction along that surface during faulting. The fault surface may or may not bear mechanical scratches from one fault block grinding against another, and it may or may not bear fibrous minerals that formed within growing voids as fault movement took place. Note that the term slickenside refers to the fault surface itself, not to any striations or mineral fibers on it, as is commonly assumed. 1072
Solid Solution Series A solid solution series is the compositional range between end-member minerals that share the same basic chemical formula but experience substitution of elements in one or more atomic sites. An example would be meionite and marialite in the scapolite group. 1081
StreakThe color of the powder produced when a mineral is drawn across unglazed porcelain. It is an aid to identification. 1073
StriatedExtremely fine lines or grooves on the face of a crystal. 1074
TabularA general term applied to the crystalline habit where the mineral consists of flat plates like the pages of a book. e.g. phlogopite mica 1075
Terminated CrystalA single terminated crystal ends in a point on one end of the crystal, whereas a double terminated crystal ends in a point on both sides of the crystal. 1005
ThermoluminescenceThe emission of visible light when a mineral is heated. Only some minerals possess this property. e.g. some Franklin fluorite (var. chlorophane). 1076
TriboluminescenceThe emission of light from some minerals, caused by either rubbing, scratching or beating. e.g. some sphalerite. 1077
VugA small cavity in a rock or mineral generally lined with crystals. 1078

Location Terms
Balls HillBalls Hill, or Balls Hill Mines, was a string of magnetite mines that was developed on the old Doland Farm in Franklin (then Franklin Furnace), New Jersey. It is located on a now partially removed hill, known locally and noted by Palache (1935) as Balls Hill. Some of the mines were specifically named: Panic, Hill, Mud, Water-Shaft, Wood, Hospital, #3, #4, and Gooseberry Mines; all are on or near Balls Hill. Bayley (1910) reported that the Balls Hill Mines were worked from 1868 to 1880. The Balls Hill Mines closed in February of 1882 (Cook, 1883). (Dunn, 2002, p.51) 1003
Buckwheat DumpAn area created to hold the waste rock from the Buckwheat and Taylor Mines. It is now a mineral-collecting site behind the Franklin Mineral Museum. 1008
Ding-dong shaftA mineshaft, now sealed, located about 250' north of the Trotter Shaft at Franklin. 1051
EdisonThe Edison Mine was developed in the 1890’s by Thomas Edison, to mine local iron ore deposits on Sparta Mountain, Sussex County, NJ, east of Ogdensburg, NJ. 1027
Farber QuarryFarber Quarry is the former name of Braen Stone Industries, a quarry that is on Cork Hill Road and within the Franklin Mining District. 1080
Franklin FurnaceThis is the old name for the early village where iron furnaces and iron mines were located, near Franklin Pond; the name was changed to Franklin, New Jersey in 1913. 1012
Franklin PondA partially man-made pond located where the early iron-mining in Franklin was centered. It is also known as the Mine Pond, Franklin Lake and Furnace Pond. Pond map1024
Hamburg MineWas an early mine on the West limb of the Franklin ore body. It was later part of the Franklin Mine and was also called the Hamburg Road Mine. It had a shaft less than 100 feet deep. 1007
Lang ShaftWas a small shaft that was 100 feet deep, located near the Hamburg Mine, north of the present High Street, Franklin, NJ. It may have been part of the Hamburg Mine, on the West limb of the Franklin ore body. 1006