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One Quarry, three Spinels

Last Updated: 5th Mar 2018

By Richard Gunter

The marble quarry, currently being worked by Kettle River Rock, is within Proterozoic Marbles of the Kettle River Complex. This is a core complex of highly metamorphosed rock brought to the surface by the north-south trending Eocene Age Granby River and Kettle River faults. The immediate area of the quarry has not been mapped in detail but the Kettle River Complex has been mapped by Cubley J.F. and Pattison D.M.R (2009): Metamorphic Contrasts across the Kettle River Fault, Southeastern British Columbia, with implications for magnitude of fault displacement. Geological Survey of Canada Current Research, 2009-9, 19p. The article contains maps of the quarry area but the quarry was not visited and is not described.

The marble quarry is excavated on a hillside exposure north of Highway #3, approximately 5 kilometers east of the city of Grand Forks, British Columbia. It has been in intermittent production since the early 1980's. The volume of production has not been large and there are few permanent structures on the property.

The marble units have a vertical orientation and strike east-west, along the edge of the bedrock ridge. The quarry has excavated the vertical beds so that a cross-section of the marble units has been exposed in the quarry wall. Within the marble units are three distinct paragenesis of spinel. These appear to be strata bound and may reflect difference in the original composition of the limestone/dolomite precursor.

Spinel 1: black colour pleonaste spinel
Image 1: black spinel
occurs as octahedrons to 2 cm. This spinel is opaque.

Spinel 2: blue colour spinel
Image 2: blue spinel
occurs as partial octahedrons to 1 cm. This spinel is translucent but not transparent.

Spinel 3: purple colour spinel
Image 3: purple spinel
occurs as isolated octahedrons to 5 mm. This is the only transparent spinel.

Each spinel has a different paragenesis. The black spinel has few silicates associated and occurs with rutile and zirconolite. The blue spinel occurs in calcite-filled pockets within massive pargasite-dravite. It occurs with rutile. The purple spinel occurs in disseminated aggregates of phlogopite. It is associated with geikielite and not rutile. The carbonate associated with all of the spinels is calcite, unlike the bulk marble which is dolomite. The major phases in the spinel-bearing bands have been identified using XRD.

The spinel-bearing marble has approximately 5% spinel in each of the occurrences and the bands are separated by non-oxide bearing dolomitic marble with forsterite (largely converted to serpentine)
Image 4: forsterite
and other Mg silicates such as Monticellite
Image 5: monticellite
which are less common and form as rims around included silicate layers.

The latest tectonism along the Kettle River Fault created open-space tension cracks in the marble. These are lined with Aragonite crystals
Image 6: aragonite
where the tension fractures intersected marble and Prehnite crystals
Image 7: prehnite
where the tension fractures intersected metamorphic clinopyroxenite.

The late-stage brittle faults also affected the quartzite-biotite schist horizon to the east of the marble. Along the brittle fault traces Chalcedony
Image 8: chalcedony
was deposited from fluids altering the quartzite. The fluids altered the interlayered biotite-sillimanite schist by hydrating the Cordierite to a fine-grained light-yellow mass of "pinnite"
Image 9: altered cordierite, sillimanite and almandine
while not altering the Sillimanite prisms or the Almandine crystals.

Article has been viewed at least 1684 times.


I clicked on the photos and the page says an error occurred. Not sure they linked properly.

Here are copied and pasted https://www.mindat.org/photo-422182.html



Interesting spinels!

Matt Neuzil
22nd Mar 2017 6:03pm
Hi Matt:

I followed the directions for the photo links so I am not sure why they did not go. You have them now.

Richard Gunter
22nd Mar 2017 6:14pm
All good. I think I have seen a problem in the past with pictures doing that. I just copied and pasted the numbers to view them. When I viewed them, I figured I'd cut and paste the web address to the pictures here so others could click the link until it resolves. No searching for others then. Looks like it's an interesting deposit.

Matt Neuzil
22nd Mar 2017 10:23pm
Great article. I have been doing a lot of work with a collection of spinels from the Rhein Property in Amity, NY and Edenville, NY. The two localities adjoin each other. Blue spinel occurs with calcite, phlogopite and clinohumite. Purple spinel occurs with serpentine, calcite and geikielite. Black spinel occurs in chondrodite. I also have purple spinel in clintonite from the clintonite type locality in Amity. This geological formation is known as the "Franklin Marble Belt" and is 20 miles north of the famous Franklin, NJ zinc mines. Thanks! Gary

Gary Moldovany
22nd Mar 2017 11:54pm
Hi Gary:

Interestingly there are no members of the Humite Group in this occurrence. There are also no identified borates or borosilicates other than Dravite associated with the blue Spinel. The "Franklin Marble Belt" may have F that this marble lacks.

Matt: Thanks for doing that. I will eventually update this with more data and will try to integrate the addresses into the article.

Richard Gunter
23rd Mar 2017 4:30pm

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