We have received numerous positive reviews from our customers over the years, below is a selection of some of our favourites.

Hello Colin, We received the lamp last Friday and I am brushing up on the equipment through reviewing "A Students Guide To Spectroscopy". Thank you for your assistance and please have a wonderful and Merry Christmas!
Brian L.G. (USA) / November, 2017

Hi Colin, My order arrived yesterday. It looks like a nice piece of kit. Thanks to you and Hillary for signing the book. I shall be getting into it this evening. Best regards.
Colin B. (Canada) / September, 2017

Hi Colin, Just to let you know that the Hylite arrived safely earlier today. I'm really excited about trying it out with the reference set A gemstones at the weekend! Thank you for all your help with my orders. Kind Regards.
Sarah B. (UK) / November, 2017

Hi Mr Winter, We have been advised your book is an excellent resource for students. I am taking the GAA course in Sydney Australia currently. I believe a few of my class may have already ordered from you. So I would very much like to get a few copies for myself. But would also be interested in a bulk lot to distribute to my classmates. Could you let me know cost for 5 copies of OPL01 Students Guide to Spectroscopy please. And of course postage. And maybe quote for 30 copies to be packed and sent. I would very much like mine signed. And maybe one or two others. Thank you.
Murray P. (Australia) / July, 2017

Hi Colin, The books are for myself Alan V. and one of my classmate Pei L. We're both currently second year gemmology students with the GAA and have found the single copy in the lab quite valuable in determining and learning the spectrum of stones and wanted to get our own copies of the book. A few others in the class have managed to find the book locally but we've not had the luck so I thought I’d go to the source! I'm both surprised and glad to hear straight from yourself! I'll leave it to you guys what you write in the dedication :) Thanks once again and i hope you have a safe trip! Regards.
Alan / May, 2017

I have received the two packages for a few days now, and the instruments are all beautifully made, and the book is full of useful tips and very nicely written. I am very happy with them. I am also impressed with the care that goes into the packaging. Many thanks for producing such quality items!
Yvonne L. (Hong Kong) / April, 2017

OPL products carry a well-deserved reputation, and ordering some is basically an investment in itself. By the way, the book (SGT Spectroscopy) is a really handy reference, well-explained.
Ivan / January, 2011

Regarding the spectroscope, the big OPL diffraction grating units are the best, particularly for seeing the 450 nm complex in sapphire (prism units stretch the blue and violet, making it tougher to see weak lines in that region).
Dick Hughes / December, 2010

Your book is absolutely amazing and even better than I imagined! It's an easy read (even for a foreigner who aren't the strongest in languages), it's very descriptive, extremely educational and I love the humour which sneak in here and there. Furthermore Hilary's illustrations are absolutely fantastic! Your little book has quickly become one of my favourites. I couldn't imagine a better guide. A real gem in my collection. It's not often I get a chance to thank an author and an illustrator directly, but here I'm jumping at the opportunity. THANK YOU BOTH, for a marvelous book, for teaching me new exciting things and for making it an easy joy starring at dark bands in a "rainbow" :o)
Hanne / November, 2010

Amazingly I have grown even happier for your book since my last mail. While comparing what I see in my little cheap spectroscope with Hilary's fantastic artwork, I've really come to appreciate the incredible amount of details you've managed to capture. It's a huge help! I've found quite a lot of very very weak lines, especially in light stones, because I knew where to look, and the paper tip are very handy in finding these weak lines as well. The little descriptions are also their weight worth in gold. I have found a single shortcoming, though. I really think this book should come with a severe warning about the addictiveness of spectroscopy.
Hanne / November, 2010

Thank you again excellent customer service... and also fine instruments.
Tapio / November, 2010

Thank you for your prompt service. All looks great, now just have to study up on how to use them... so glad I purchased the book as well.
Andrew / July, 2010

It would be a great honor for me to receive an autographed copy of your book! It appears your work is highly regarded since I checked with those whom I respect and your book was the only one suggested as the best.
Leo / June, 2010

I was so surprised when I got home from work yesterday and Fed Ex came with my package! I was expecting it to take a week or so. Thank you so much for getting it out so quickly. I have spent all morning reading your book and making my first attempts at using the spectroscope. I appreciate all you help.
Christine / March, 2010

All three (packages) arrived in good order thanks to your/someone's excellent packaging skills. They were all so well padded and wrapped obviously by a very experienced packer, and it was very exciting demummifying them to find the instruments intact. So thank you, and especially for having to fiddle around with three separate packages.
Julie / January, 2010

Hi Colin, I have heard these are the BEST spectroscopes out there and I need to build my lab since I'm a distant ed. student at GIA, Carlsbad
Thank you!
Donna / April, 2008

Hello, I would like to buy the opl teaching spectroscope and the 'little' book to accompany it. Highly recommended by the folks on gemologyonline.com.
Todd / April, 2008