Deleted
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Post by Deleted on May 8, 2017 22:25:59 GMT -5
This is a sort of reverse ID thread. I have discovered I truly like cubic crystals. 1dave showed me a very nice magnetite crystal specimen. I had my eyes on a halite specimen too. So I want start a list of crystals of cubic habit. Halite Magnetite Flourite Pyrite (thanks Pat!) Diamond (thanks again Pat!) Can anyone help me grow a list? I may look at a cabinet of cubes!
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Post by Pat on May 8, 2017 22:48:10 GMT -5
Diamond Fluorite Pyrite
I just googled cubic crystals. Probably more. They are interesting.
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Post by 1dave on May 8, 2017 23:41:59 GMT -5
Sorry Scott, I lied to you. Magnetite was right below what you picked up - Iron Pyrite altered to Goethite.
From Dan's Textbook of Mineralogy:
Metallic Luster: Galena, Iron Pyrite
Nonmetallic Luster: Flourite, Cuprite, Creargyrite, halite, Sylvite, Boracite, Pharmacosiderite, Percylite, Perovskite.
Cube-like: Apophylite, Cryolite, Chabazite, Alunite, Calcite, rarely Quartz and Hematite.
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Post by captbob on May 9, 2017 8:40:43 GMT -5
Be a real stretch to include magnetite in the cubic family. More triangular. I have seen azurite and wulfenite with cubic crystals, but that is certainly not their normal growth pattern, wouldn't count them in your cubic group either. True cubic mineral specimens are truly a very limited family. Pyrite, fluorite and galena being your best examples. Probably some rarer minerals that form in cubes, may think of more once I quit trying to think of them. (like trying to recall someone's name!)
Siderite ... meh, more often not.
Don't spend a bunch on a quality halite specimen if it is humid where you live.
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Deleted
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Post by Deleted on May 9, 2017 22:43:39 GMT -5
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Post by Deleted on May 9, 2017 22:44:40 GMT -5
Be a real stretch to include magnetite in the cubic family. More triangular. I have seen azurite and wulfenite with cubic crystals, but that is certainly not their normal growth pattern, wouldn't count them in your cubic group either. True cubic mineral specimens are truly a very limited family. Pyrite, fluorite and galena being your best examples. Probably some rarer minerals that form in cubes, may think of more once I quit trying to think of them. (like trying to recall someone's name!) Siderite ... meh, more often not. Don't spend a bunch on a quality halite specimen if it is humid where you live. No humidity here. But I'm not a true specimen collection I would coat it with clear coat or something to protect it.
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Post by captbob on May 9, 2017 23:44:11 GMT -5
On the page from the Betts site it says "rare cubic". That's exactly correct - rare. That's why I wouldn't include magnetite in your cubic group. The cube isn't its natural / normal shape. Just as I have seen "cubic" azurite and wulfenite. Heck, I have seen cubic sulphur crystals, but they are not the norm. Mother Nature does some odd things! Your collection, collect what you want. Good luck finding a magnetite cube for your shelf! It would be darn small if found. Here's some of my pyrite collection - I like cubes too! a big chunk - lousy picture Went through a fluorite phase years back, oh... and a galena phase, and a magnetite phase, and ... (it's what I do) Always wonder what will strike my fancy next.
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Post by captbob on May 9, 2017 23:52:46 GMT -5
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Post by 1dave on May 10, 2017 9:50:18 GMT -5
A = what @shotgunner picked up. Iron Pyrite altered to Goethite - From Pelican Point - west side of Utah Lake. B = what I thought he picked up.
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Post by melhill1659 on May 10, 2017 10:51:17 GMT -5
On the page from the Betts site it says "rare cubic". That's exactly correct - rare. That's why I wouldn't include magnetite in your cubic group. The cube isn't its natural / normal shape. Just as I have seen "cubic" azurite and wulfenite. Heck, I have seen cubic sulphur crystals, but they are not the norm. Mother Nature does some odd things! Your collection, collect what you want. Good luck finding a magnetite cube for your shelf! It would be darn small if found. Here's some of my pyrite collection - I like cubes too! a big chunk - lousy picture Went through a fluorite phase years back, oh... and a galena phase, and a magnetite phase, and ... (it's what I do) Always wonder what will strike my fancy next. Oh my gosh... I was so proud of my perfectly formed pyrite cube I found last week (it's like mm size) until I see yours LOL
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unclesoska
freely admits to licking rocks
All those jade boulders tossed in search of gold!
Member since February 2011
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Post by unclesoska on May 10, 2017 11:18:44 GMT -5
I have some small jars full of cubic hematite if anyone's interested, P.M. me- I have no use for them. Might post a pic later
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Post by 1dave on May 10, 2017 13:01:00 GMT -5
I have some small jars full of cubic hematite if anyone's interested, P.M. me- I have no use for them. Might post a pic later @shotgunner Hop on this!
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gemfeller
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Post by gemfeller on May 10, 2017 15:03:38 GMT -5
On the page from the Betts site it says "rare cubic". That's exactly correct - rare. That's why I wouldn't include magnetite in your cubic group. Sorry Capt., but minerals don't crystallize in more than one geometric system. Magnetite is cubic, as defined by having 3 axes of equal length intersecting at 90 degrees. When in doubt I go to the mineralogy experts like Frederick H. Pough who describes it as "Cubic - hexoctahedral" and Walter S. Schumann "Cubic." Other authoritative resources define it as cubic. Cubic crystals can form in many "habits" like garnet, that don't outwardly resemble neat little cubes. But when analyzed they all have identical geometry and fall into the isometric system.
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Post by 1dave on May 10, 2017 15:07:24 GMT -5
Cubic, but not necessarily cubes.
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Post by captbob on May 10, 2017 15:57:51 GMT -5
Cubic, but not necessarily cubes. aaah... here I am thinking in terms of "cubic" being a square cube. I have a butt load of magnetite, and their formation is primarily more triangular or like two triangles butted together at the base. More like the specimen on the left in the John Betts picture below that Scott posted. I don't consider such cubes, but if folks with much fancier names than I have want to call them cubic, who am I to disagree? One of my magnetite specimens with triangular cubic thingys So is a pyramid "cubic"?
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gemfeller
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Post by gemfeller on May 10, 2017 16:34:39 GMT -5
Capt., maybe this will help in visualizing the matter. The word "cubic" may be a little misleading because one automatically thinks of a cube, not a variation. But all of the following follow the rule: 3 axes of equal length intersecting at right angles, i.e., cubic.
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gemfeller
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Post by gemfeller on May 10, 2017 16:41:53 GMT -5
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jamesp
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Post by jamesp on May 11, 2017 5:50:25 GMT -5
Cubic Zirconia Salt Rubik's cube dice galena got mentioned " They crystallize in the cubic system, having three axes that are all of equal length and perpendicular to each other. Garnets do not show cleavage, so when they fracture under stress, sharp irregular pieces are formed (conchoidal)." What good is a garnet if it don't show cleavage ? There's that conchoidal word again. captbob, your cubics are off the chart. Those pyrites. Salt crystals Not referring to captbob, sponge head:
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unclesoska
freely admits to licking rocks
All those jade boulders tossed in search of gold!
Member since February 2011
Posts: 934
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Post by unclesoska on May 11, 2017 9:30:31 GMT -5
I was told by a rock club member that these were Hematite. During photography, I got curious and did a couple physical tests- streak: reddish brown/brown. Hardness: >7. Habit: isometric (cubic). Color: brown/black. Lustre: submetalic? The hardness alone indicates it is NOT hematite, but that's as far as I got late last night. Educated guess' welcome!
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Post by rockpickerforever on May 11, 2017 9:38:11 GMT -5
I was told by a rock club member that these were Hematite. During photography, I got curious and did a couple physical tests- streak: reddish brown/brown. Hardness: >7. Habit: isometric (cubic). Color: brown/black. Lustre: submetalic? The hardness alone indicates it is NOT hematite, but that's as far as I got late last night. Educated guess' welcome! Looks like Limonite to me.
I have some pieces that remind me of the graphite/carbon brushes used in older electric motors.
Before the throwaway days, you used to be able to replace them to get more miles out of your motors.
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