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Identity HelpNot sure, sold to me as topaz, identify please?

26th Jun 2017 15:51 UTCJerry Morgan

Hardness at least 7 1/2, thanks folks...

26th Jun 2017 16:10 UTCAndrew Haighton

Hi Jerry;

Looks like Topaz from Thomas Range, Utah to me.

It's the white inclusions which is the giveaway, as well as the colour.

Enjoy.

26th Jun 2017 16:16 UTCDonald B Peck Expert

Hi Jerry,

I am not sure, but in the first photo the crystal appears to be monoclinic. Topaz is orthorhombic, which fits the 2nd and 3rd photos OK. But the 1st one kind of spoils that. Otherwise it does look like a topaz. How hard is the crystal? If a shard of quartz will not scratch it, it could be topaz. (try a very small scratch . . . on the base, if you can, and inspect with magnification).

Don

26th Jun 2017 17:04 UTCJerry Morgan

Thanks folks...

Quartz will not scratch it. I too am puzzled by the monoclinic vs orthorhombic

I have dusted off my triple beam balance and am trying to locate my graduated cylinder, specific gravity will be next.

My intention is to split it, top to bottom and make two necklace pendants. Hate to offer for sale as topaz, if it's not...

If unable to ID with certainty, I'll just add to my collection of "keepers"...

jerry

26th Jun 2017 17:14 UTCryan christensen

Looks like Topaz from San Luis Potosi, Mexico

26th Jun 2017 18:43 UTCOwen Lewis

Hi Jerry,

A skewed rhombus cross section in topaz is not so unusual as to have stopped me from having more then one such in my small collection. 80% certain that yours is topaz. Quartz won't scratch it - but will it scratch quartz? A SG close to 3.51 would make it conclusive for me. IMHO, not from Thomas Range UT though; San Luis Potosi, Mexico looks possible from those (few) I have seen from there.

Good luck with your plan to split it lengthwise! Topaz having a perfect basal cleavage only.... I think I can see a couple of incipient basal cleavages in your second pic. Great shots from a phone camera and hand-held subject by the way!

26th Jun 2017 20:38 UTCAlfred L. Ostrander

In the bottom picture you can clearly see the distortion to forms making up the termination. This has distorted the orthorhombic nature of the crystal. Owen said it well calling it skewed.

26th Jun 2017 21:24 UTCIan Nicastro

I totally agree with Ryan and Owen, classic Topaz from San Luis Potosi, Mexico

27th Jun 2017 13:36 UTCJerry Morgan

Thanks for the input folks, appreciate it more than you know. Really cool to have a place to get info and watch the collective knowledge being shared...

Owen, I am not a gemologist... more like a dusty, dirty rock collector with a very strong desire to create jewelry. I will use a diamond saw on my lapidary.....

Thanks, Guys...

jerry

27th Jun 2017 14:00 UTCHarold Moritz 🌟 Expert

100% topaz, crystal forms are right on. Topaz crystallizes in the Rhombic-Dipyramidal class of the orthorhombic system. First photo is looking down the c-axis, showing pinacoid terminal face. Second photo shows the 3rd order prism faces. Third photo shows pyramidal faces around the terminal pinacoid face. The crystal shows orthorhombic symmetry because the pinacoid face is at right angles to the prism faces, and the prism faces have two pairs of equally-developed, parallel faces that intersect at unequal distances from center, thus the three symmetry axes are of different lengths, but all at right angles to each other. Most topaz crystals display a prism with a rhombic cross-section (in line with the symmetry class name). I've collected hundreds in Trumbull, Conn., it is one of the easy ways to tell it apart from quartz. There is no distortion in this nice pocket crystal. The a and b symmetry axes are intersecting the lines where the 3rd order prism faces meet. In other orthorhombic forms the axes intersect the midpoint of the faces, these are sets of pinacoid forms, in which case the prism's cross-section would be rectangular rather than rhombic. Usually the crystal will show both forms combined, with the prism faces dominant.

27th Jun 2017 15:48 UTCDonald B Peck Expert

Jerry and Harold,

Thank you. I just learned something. Harold, I was unaware of the crystallography of topaz. Now I need to read it again and try to digest it.

Don

27th Jun 2017 17:41 UTCAlfred L. Ostrander

Harold, as you say, the third photo shows the pyramidal faces between the prism and the terminal pinacoid. However, what I see is what I desceibed as distorted growth. There appears to be, at a minimun, irregular, or shall I say less the textbook perfect crystallography. If this is, as I suspect, some of the natural vagaries of crystal growth that lead to distorted or irregular appearing growth that can affect the geometric shape of a face leading to an appearance that perhaps suggested monoclinic rather than orthorhombic crystallization. The outline of that pinacoid is distorted from a texbook point of view. From that one perspective the crystallographic axes appear to some as not being normal one to another. Your description was spot on, relating the axes to the prism in relationship to the other forms. You and I know from hard experience that all forms present must be accounted for. Then an odd or as I said "distorted" face will make sense. I bring this up as it is surprising how many people wonder why pyrite isn't orthorhombic because the crystals they often see are not perfect cubes. Or why all faces of the prism of a quartz crystal aren't the same size.

So was distorted an erroneous term, as I certainly do see very less than perfect textbook form. It has been my experience that people not well versed in crystallography see the natural variations and don't do very well matching up said variations to the textbook. Your observations and identifications are always to be respected. My background includes referring to irregular shapes as distortions. If you have a better word, I would appreciate your insight. Or is skewed, as Owen suggested a better word?

27th Jun 2017 18:00 UTCHarold Moritz 🌟 Expert

Alfred:

Thanks. Shrug, only so much one can easily discern accurately from 2D photos...but few crystals are textbook perfect. Distortion is as good a general term as any, though I still dont really see how this one is (could be the camera lens used). No matter, there is enough here to tell it is topaz, all I was trying to get at. Thankfully Jerry put up several, well lit and sharp pix from different angles (y'all know the dark, blurry, horribly color-unbalanced, single photo of specimens we are used to dealing with on these ID forums!), though as a general comment, taking them a LOT closer to the crystal would help...

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