Minerals M-Z from the Lime Crest and Farber Quarries

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Quarry minerals A-L

MAGNETITE: I've found tiny, sharp octahedrons at Lime Crest.  Magnetite is in the spinel group, but it's perfectly opaque-- and magnetic.

MARGARITE: Bright lime-green or bluish-green micaceous / foliated masses. More commonly, dull gray. Found at the Franklin ("Farber") quarry in moderate amounts, usually with a light brown variety of mica (phlogopite?) and sometimes with rutile. Margarite adds color to your daylight mineral collection, but good specimens showing vivid color are very uncommon.

MOLYBDENITE: silvery, thin, hexagonal plates and scales, easily confused with graphite, occur at the quarries. Molybdenite can form elongated, "barrel"-shaped crystals which have perfect basal cleavage (much like mica crystals). I have not found any of these yet from the Sussex Co. quarries.  This morphology would be easiest to distinguish from graphite, but when they're just individual flakes, it's a bit tougher.  Molybdenite is of course a sulfide, so there's always the chemical tests.

NORBERGITE and CHONDRODITE: Yellow to honey-brown, found as multiple grains in the altered limestone in both the Franklin and the Lime Crest quarries. Some norbergite specimens are exceptionally fluorescent (yellow under SW), and some occur with brightly-fluorescent (bluish-white SW) grains of DIOPSIDE. Occasionally you'll find a well-formed, small crystal of chondrodite or norbergite, but the majority are anhedral or just misshapen and with poorly-defined faces.

PYRITE: May occur as pyritohedrons or cubes at the Lime Crest and Franklin quarries. Some of the pyrite cubes from the Franklin quarry were fairly large (5 mm to 1 cm). Lime Crest produces strangely elongated pyrite crystals which appear to be drastically stretched pyritohedrons. The longest one I've seen was about 1 cm in length and 2 mm in width, but this was unusual.
Pyrite dissolves slowly or not at all in hydrochloric (muriatic) acid.

PYROCHLORE - MICROLITE: Suspected (by me!), though I've never had it analyzed.  Overall appearance, waxy to glassy luster, and mild radioactivity are all I'm going on.  These minerals (and euxenite, et al.), are literally a mess to determine. They have no definite crystal structure (i.e., they are metamict) and only full quantitative analysis can tell them apart.  Come to think of it, only certain types of instrumental analysis are really of any use.  A full quantitative chemistry workup would be ideal, if you could obtain a large enough sample (and a good analytical balance, along with the reagents necessary to separate out the rare-earths).

PYRRHOTITE (Hardness: 4; Streak: black; Gravity: 4.6 to 4.7; Other: dust is magnetic)
Pyrrhotite looks like pyrite but is usually duller in hue. When found, crystals have a hexagonal cross-section. It dissolves easily in hydrochloric (muriatic) acid, generating foul and poisonous hydrogen sulfide gas.  The fact that small particles are magnetic is usually sufficient to distinguish pyrrhotite from other sulfides.

QUARTZ: We have found no crystals yet, but tons of the massive form. Much of it is smoky quartz. Often found in "boudins" containing scapolite (meionite); the rock around the boudin is calcite (marble). Some crystals of allanite, titanite, and other minerals are locked inside quartz, making them hard to expose without breaking them.

RHODONITE: I've heard rumors of this mineral occurring at Lime Crest. Crystals would be rare, I'm sure. I have yet to see a piece of definite rhodonite found at Lime Crest or any other local marble quarry.  I can understand why someone might have thought they'd found rhodonite at Lime Crest;  consider this pink mineral I found at a Lime Crest trip (2000 or 2001):

Is this rhodonite? Some tests might tell us.

Guess what, though... it's not rhodonite.  I found it in the far end of the quarry, in a rockpile on the quarry floor. The rockpile was mostly a broken-up "pegmatite" body which had a pyrochlore or microlite-like mineral with the typical radial fractures in quartz. This pink "rhodonite" look-alike: what is it?  There was a flyer that they used to give out at the field trips which listed rhodonite as one of the minerals that was found in this marble quarry; was the pink mineral shown above the same thing they had found?  Is it rhodonite? Probably not... here's a qualitative analysis of this specimen. Some simple tests suggest it's scapolite (see below).  Comparing the fracture surface with known scapolite specimens tends to support this.

RUTILE can occur as tiny needles, though some specimens occur in the Lime Crest rock as tabular crystals. I have one such crystal which is approximately 1.5 mm across. The Franklin quarry produces elongated rutile crystals or needles, sometimes found with margarite.

SCAPOLITE (probably MEIONITE): One of my favorite minerals... It occurs in massive form, but at least one collector found a nice crystal of it last time at Lime Crest. The crystal was a couple of centimeters long, so I'm sure you could find micromount-grade scapolite crystals if you searched enough at that quarry. Scapolite can be gray-green, light apple-green, gray, white, pinkish, yellow, or brownish. Note: most scapolite from Franklin and surrounding areas is probably meionite or an intermediate composition of meionite-marialite (with the composition slanted toward meionite). Pure, end-member marialite is fairly rare at Franklin.

SCHEELITE: I almost forgot to mention this mineral, since I have not found large quantities of it (yet).
There is no mistaking the fluorescent response of scheelite in its pure (molybdenum-free) state: brilliant white under SW. I have found tiny spots of this mineral in Lime Crest, most often associated with the scapolite (meionite). Scheelite does occur in the Franklin marble;  a collecting buddy of mine has a good specimen of fluorescent scheelite from Lime Crest that would otherwise have ended up in the crusher.

SPHALERITE: Zinc sulfide. Forms brown, yellow, black, oil-green, or reddish-brown tetrahedral crystals, often sharply formed. Broken surfaces have a very high luster. There was a Mississippi Valley-Type mineralization area found in the Lime Crest Quarry which contained translucent yellow sphalerite, along with fluorite, galena, and some barite.

SPINEL: red ("ruby spinel") grading to black ("pleonaste") varieties occur at the Lime Crest Quarry. Deep purple seems to be the most frequently-encountered color of spinel here. A well-formed spinel octahedron is a real prize for a day's collecting, even if the crystal is only a couple of millimeters across. Spinel is usually translucent to nearly opaque, but exceptional ones could be transparent. It has a specific gravity of 3.5 to 4.1

THORITE: Similar to allanite in appearance when in massive form, but more radioactive. It is usually brown or black but can also be orange-red or brick red (uncommon). Thorite is of the tetragonal crystal system but can form pseudocubic crystals. It can also occur as needle-like (acicular) crystals. Thorite specimens have been found at Lime Crest. The best way to find thorite is with a radiation detector or Geiger counter. Thorite is a silicate of Th and can also contain some U.

TITANITE (SPHENE): brown, somewhat shiny, wedge-shaped crystals up to 1 cm have been found at Lime Crest. Many nice crystals of 1 to 3 mm occur there, making for some pleasing micromount specimens. The trick is not to break the crystals while exposing them from matrix! They are fragile. I estimate that 90% of them break while "taking apart" a rock... maybe 95%. The matrix is really tough stuff, a lot of quartz, so you can't just scrape it away with a dental pick.  Neither can you etch it away with acid.  It really comes down to luck.

TOURMALINE var. DRAVITE: (Streak: colorless; Hardness: 7 to 7.5; Gravity: 3 to 3.3; Other: insoluble in acids)
Striated, brown, prisms with "bulged triangular" cross-section occur at the Lime Crest Quarry. More common is the massive form of this mineral, which is also brown or reddish-brown. Tourmalines become electrically charged upon heating (and letting cool); at this point they will attract tiny bits of dry paper or dust.

TOURMALINE var. UVITE: (Streak: colorless; Hardness: 7 to 7.5; Gravity: 3 to 3.3; Other: insoluble in acids)
Light green uvite occurs as isolated crystals in the Franklin quarry. Some larger (1 cm), well-crystallized specimens have come out of there, but the only ones I've found were small, anhedral or subhedral grains. Even these are worth keeping, since they are unusual, have a pleasing color, and fluoresce yellow-orange under UV light.
The only fluorescent tourmaline I have is a piece I kicked out of the dust on the Farber quarry floor while heading back to the entrance. I do not know if it is uvite or dravite, but it is almost certainly tourmaline. A lucky find!

TREMOLITE: Colorless, white, gray, or bluish-gray crystals occur in the area quarries, often as sprays or clustered, flattened prisms. Can also be massive or in grains.Sometimes this tremolite is highly fluorescent (bluish-white SW), but much of it is not. There are some large boulder piles in the middle of the Franklin quarry which contain fluorescent tremolite crystals.
The shortwave color of tremolite is very similar to that of fluorescent DIOPSIDE, also found at area quarries. NOTE: That's probably because it IS diopside; we think these fluorescing "tremolite" specimens to be pseudomorphs of fluorescent diopside after tremolite.
I have NEVER found any of the supposed "asbestiform tremolite" that served as one of the weak excuses in getting the quarry shut down by a bunch of newcomers to the area. We have looked at many, many tons of rocks in many field trips to the Lime Crest and Farber quarries and have not found ANY of this "asbestos-like" material. You can bet if I ever found any, I'd take it home to put in my collection!  Fibrous tremolite, crocidolite, etc. would stand out very obviously to us, the ever-alert field collectors who are always on the lookout for interesting or "different" varieties of minerals. So as far as I'm concerned, the whole ruckus about "asbestiform tremolite" was completely bogus.  Of course, the "revisionist" version of what happened at Lime Crest is that a multinational bought the place to shut it down.  To  believe that, you'd also have to believe that the cost of shipping bulk aggregate from overseas is somehow less than quarrying it in the USA for local markets.  Unless there's some bizarre economic reality of which I'm unaware, that sounds highly implausible.  Of course, a multinational could very well have bought the distressed Lime Crest Quarry, knowing full well that it could no longer be operated due to what had happened.  That's the most likely scenario.

ZIRCON: (Streak: colorless; Hardness: 6.5 to 7.5; Gravity: 4.0 to 4.7; Cleavage: imperfect, 2 directions; Other: often fluorescent yellowish, SW; may be weakly radioactive)
Found in pegmatite bodies and in impure limestones, so the Lime Crest / Farber quarries are likely places. Can be anywhere from transparent to nearly opaque. Crystals can be elongated; many have ends terminating as 4-sided pyramids. Zircon crystals are loners and do not associate much with other zircon crystals.
Many years ago, Lime Crest zircons were found as brown crystals with a bluish coating.
Note: finally, a mineral that occurs almost exclusively in crystallized form. The question is, how well-formed will the crystals be?

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