Virtually all the Umba Sapphires show a unique 'color-change'. That is, they appear to be one color in daylight and another under incandescent light. All due to the amounts of chrome in the stone.
Umba Sapphires must be the most difficult stones to describe color, because of the color-change' phenomena. These are no exception. I have tried my best to convey the colors seen firstly in natural light and next the change shown under artificial light. Because the stones are strongly dichroic, I have described the predominant color.

MADAGASCAR GLASS-FILLED RUBIES (see Ruby GF) We have some new stock of these stones - all the material offered at $85.00 per ct - sent to us on consignment, to test the market. This color is much better than our previous material, showing a rich red color, but, of course, with inclusions. Read on to understand and to become fully conversant as to what 'Glass Filled' means.
First some background - Madagascar miners have been finding large deposits of a dark red Ruby, so dark that much of it couldn't be utilized in cutting. For the last few years, the cutters in Thailand have been working on a process to lighten this Ruby. .The rough is treated , together with lead glass, in a very high, prolonged heat process and under a strong vacuum. This has resulted in the superb red-pink color which shows amazing fluorescence under incandescent light. The lead glass, I am told, was supposed to fill any fractures. Under a microscope, some actual fusion of cracks has been noted in similar rough so you can imagine the heat these stones are subjected to. This treatment is now being used for the new Ruby deposits found in Mozambique. The upshot is that, although these Rubies are treated, they are not synthetic and cost a fraction of what you would pay for untreated stones of similar color.
More of these stones (larger sizes) on our Tanganyika Trading plate
Click onto www.gia.edu/research-resources-from-research/index.html for further information and for the comments regarding this process and their suggested wording for the treated/cut stone

Ruby - Glass filled

TANZANITES -these stones are from Tanganyika Trading and are direct from the mine to the buyer. Some cleaning has been done but not to the degree as those stones from African Gemstones.

The majority of the cut Tanzanites found today are heat-treated from rough which has a natural brownish-yellow color, sometimes with a blue or purple overtone. This rough, on heating, WILL change to the beautiful richer blue to purple-blue colors Tanzanite is generally known for. However, there is a small segment of Tanzanites which show the natural blue-purple-turquoise color combinations, rarely seen in jewelry. This unique, natural material is what we offer. None of the rough has been irradiated, heat-treated or enhanced in any manner. These stones do not show as strong a color as their heat-treated cousins but show some of the different color combinations you can find in Tanzanite. Personally, I rather like this type of Tanzanite - it is quite unique (something which always appeals to me) and definitely of interest to the purist. Tanzanite is known as a 'triclinic' mineral, that is, it is one of the very few gems that shows three separate colors which are often quite distinct from each other.

TAKE A LOOK AT THE TANZANITES OF SIMILAR COLOR ON OUR ARCHIVES LIST BELOW - Compare the difference in price - now is the time to start considering putting some money into this gem

Ref	Status	Grade/Total	$ per	Total	Stone	Color	Country
No.		weight	carat	price	type	and remarks	of  origin
1	sold	5.19 ct AA	$55.00	$285.00	Sapphire	Winza - a medium-light pink stone	Tanzania
2	sold	6.91 ct AA	$60.00	$415.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
3		4.54 ct AA+	$18.00	$40.00	Sapphire	a pretty, medium-strong blue stone	Nigeria
4		7.53 ct AA	$50.00	$377.00	Sapphire	a medium-light blue to light purple change	Tanzania
5		5.42 ct AA	$50.00	$271.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
6		6.04 ct AA	$45.00	$272.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
7		3.80 ct AA+	$25.00	$95.00	Sapphire	a beautiful clear medium blue, slight zoning	Madagascar
8		3.69 ct AA	$25.00	$92.00	Sapphire	a medium blue to light purple color change	Tanzania
9		5.12 ct A+	$85.00	$435.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
10		4.44 ct A+	$85.00	$377.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
11		5.58 ct AA	$35.00	$195.00	Sapphire	a medium-light blue to light purple	Tanzania
12		4.74 ct A+	$50.00	$237.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
13		4.45 ct AA	$30.00	$134.00	Sapphire	a medium-light blue to light purple	Tanzania
14	sold	7.05 ct AA	$60.00	$423.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
15		3.74 ct AA+	$32.00	$120.00	Sapphire	a medium-light purple-blue color	Madagascar
16		3.95 ct AA+	$18.00	$71.00	Sapphire	a pretty, medium-strong blue to white stone	Nigeria
17		6.63 ct AA+	$35.00	$232.00	Sapphire	a lovely, medium-light blue color	Madagascar
18		6.37 ct AA	$35.00	$223.00	Sapphire	a medium-light blue to light purple	Tanzania
19		3.64 A+	$43.00	$157.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
20		4.79 ct AA	$30.00	$144.00	Sapphire	a medium blue-purple to purple change	Tanzania
21	sold	4.54 ct AA+	$18.00	$82.00	Sapphire	a pretty, medium-strong blue stone	Nigeria
22		2.54 ct A+	$40.00	$102.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
23		7.03 ct AA	$35.00	$246.00	Sapphire	a medium-light purple-blue to light purple	Tanzania
24		3.85 ct A+	$40.00	$154.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
25		4.00 ct AA+	$18.00	$72.00	Sapphire	a pretty, medium-strong blue stone	Nigeria
26		4.10 ct AA+	$18.00	$74.00	Sapphire	a pretty, medium-strong blue stone	Nigeria
27		5.06 ct AA	$55.00	$278.00	Sapphire	Winza - a stronger purple-pink color	Tanzania
28		3.95 ct AA	$25.00	$99.00	Sapphire	a medium-light blue - no color change	Tanzania
29		5.96 ct AA	$50.00	$298.00	Sapphire	a medium blue to purple change	Tanzania
30		2.67 ct AA	$18.00	$48.00	Sapphire	a medium lilac-blue to purple-pink change	Tanzania
31		4.19 ct A+	$50.00	$210.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
32		4.36 ct AA	$35.00	$153.00	Sapphire	a medium purple-blue to purple change	Tanzania
33		4.78 ct AA+	$18.00	$86.00	Sapphire	a pretty, medium-strong blue to white stone	Nigeria
34		3.10 ct AA+	$18.00	$56.00	Sapphire	a pretty, medium-strong blue stone	Nigeria
35		3.58 ct AA+	$18.00	$64.00	Sapphire	a pretty, medium-strong blue stone	Nigeria
36		4.09 ct AAA	$36.00	$147.00	Tanzanite	shows good medium purple and blue colors	Tanzania
37		6.38 ct AAA	$32.00	$204.00	Tanzanite	medium to light purple and blue colors	Tanzania
38		6.25 ct AAA	$30.00	$123.00	Tanzanite	shows lighter purple and blue colors	Tanzania
39	hold	12.16 ct AAA	$60.00	$730.00	Tanzanite	shows good medium purple and blue colors	Tanzania
40	sold	5.70 ct AAA	$36.00	$205.00	Tanzanite	shows good medium purple and blue colors	Tanzania
41	sold	11.38 ct AAA	$70.00	$797.00	Tanzanite	shows good medium purple-blue colors	Tanzania
42		5.30 ct AAA	$30.00	$159.00	Tanzanite	med/ light purple, turquoise blue, light blue	Tanzania
43		9.72 ct AAA	$30.00	$292.00	Tanzanite	med. to light, purple, turquoise, purple-pink	Tanzania
44		5.38 ct AAA	$36.00	$194.00	Tanzanite	med. to light, blue, purple, purple-pink	Tanzania
45		11.00 ct AAA	$70.00	$770.00	Tanzanite	shows good medium purple-blue colors	Tanzania
46		4.51 ct AAA	$32.00	$231.00	Tanzanite	medium to light purple and blue colors	Tanzania
47		8.47 ct AAA	$36.00	$305.00	Tanzanite	med. to light, turquoise, blue, purple	Tanzania
48		5.60 ct AAA	$33.00	$185.00	Tanzanite	med. to light purple, turquoise, purple-pink	Tanzania
49		7.94 ct AAA	$30.00	$238.00	Tanzanite	med. to light, purple, green, purple-pink	Tanzania
50		6.53 ct AAA	$30.00	$196.00	Tanzanite	light purple-pink, med. purple, blue	Tanzania
51		8.51 ct AA+	$30.00	$255.00	Tanzanite	purple-pink, purple, blue-green - cut 2 stones	Tanzania
52		9.02 ct AA+	$33.00	$298.00	Tanzanite	med. to light purple, turquoise, purple-pink	Tanzania
53		6.91 ct AA+	$30.00	$207.00	Tanzanite	med. to light, blue, purple, purple-pink	Tanzania
54	sold	10.18 ct AAA	$70.00	$713.00	Tanzanite	shows good medium purple and blue colors	Tanzania
55		4.55 ct A+	$85.00	$387.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
56		4.89 ct A+	$85.00	$416.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
57		4.08 ct A+	$50.00	$204.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
58		7.74 ct AA	$40.00	$310.00	Sapphire	a medium light blue - no color change	Tanzania
59		3.16 ct AA+	$36.00	$114.00	Sapphire	a beautiful, bright pink, note. 3.5mm thick	Madagascar
60		4.26 ct A+	$50.00	$213.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
61		7.47 ct AA	$45.00	$336.00	Sapphire	a medium light blue to purple change	Tanzania
62		7.07 ct A+	$60.00	$424.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
63		3.94 ct A+	$40.00	$118.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
64		4.04 ct AA	$30.00	$121.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
65		4.31 ct AA	$30.00	$121.00	Sapphire	Winza - a stronger, deeper pink color	Tanzania
66	sold	5.98 ct AA	$60.00	$359.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
67		4.94 ct AA	$30.00	$148.00	Sapphire	a light blue to light purple change	Tanzania
68		4.08 ct AA+	$30.00	$122.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
69		3.96 ct AA	$10.00	$40.00	Sapphire	a medium-light blue stone, touch gray	Tanzania
70		3.18 ct A+	$40.00	$127.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
71		2.86 ct A+	$40.00	$114.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
72		2.82 ct A+	$40.00	$113.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
73		4.30 ct A+	$85.00	$366.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
74		3.82 ct AA+	$38.00	$145.00	Sapphire	a strong, blue-purple to purple-pink	Tanzania
75		4.16 ct AA	$30.00	$125.00	Sapphire	a medium light blue - no color change	Tanzania
76		7.59 ct AA	$40.00	$304.00	Sapphire	a medium blue to purple change	Tanzania
77		4.13 ct AA	$30.00	$124.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
78		4.25 ct AA+	$30.00	$128.00	Sapphire	a bright, light blue stone	Madagascar
79		5.65 ct AA	$35.00	$198.00	Sapphire	a medium-light blue to purple change	Tanzania
80		4.82 ct A+	$85.00	$410.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
81		4.86 ct AA	$45.00	$219.00	Sapphire	a medium purple-blue to purple change	Tanzania
82		4.39 ct A+	$50.00	$220.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
83		4.12 ct AA	$15.00	$62.00	Sapphire	a medium purple-blue to purple change	Tanzania
84		4.19 ct A+	$50.00	$210.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
85		4.14 ct AA	$30.00	$124.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
86		4.98 ct AA	$30.00	$149.00	Sapphire	a medium-light blue to light purple change	Tanzania
87		5.16 ct AA	$35.00	$181.00	Sapphire	a light blue to purple change	Tanzania
88		3.83 ct AA	$20.00	$77.00	Sapphire	a medium light blue to purple change	Tanzania
89		5.25 ct AA	$50.00	$263.00	Sapphire	a medium purple-blue to purple change	Tanzania
90		4.97 ct AA	$25.00	$124.00	Sapphire	a medium light purple to purple-pink color	Tanzania
91		4.82 ct A+	$85.00	$410.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
92		4.46 ct AA	$25.00	$112.00	Sapphire	a medium blue to purple change	Tanzania
93		5.44 ct A+	$85.00	$462.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
94		6.02 ct AA	$25.00	$151.00	Sapphire	a medium purple-blue to purple change	Tanzania
95		5.08 ct A+	$50.00	$254.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
96		4.30 ct AA	$30.00	$129.00	Sapphire	a medium purple-blue to purple change	Tanzania
97		3.58 ct A+	$40.00	$143.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
98		3.14 ct A+	$25.00	$79.00	Sapphire	a bright medium blue, central black inclusion	Madagacar
99		6.46 ct A+	$85.00	$549.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
100		3.64 ct A+	$85.00	$309.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
101		3.01 ct AA	$20.00	$60.00	Sapphire	a medium-light purple-blue to purple	Tanzania
102		4.79 ct A+	$50.00	$240.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
103		4.24 ct AA	$30.00	$127.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
104		4.07 ct AA	$30.00	$122.00	Sapphire	stronger blue and purple change to purple	Tanzania
105		3.34 ct A+	$43.00	$144.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
106		3.56 ct AA	$30.00	$107.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
107		4.08 ct AA	$30.00	$110.00	Sapphire	Winza -shows a mix of pink and blue colors	Tanzania
108		6.00 ct AA	$40.00	$240.00	Sapphire	a light purple-blue to purple change	Tanzania
109		3,.28 ct A+	$43.00	$141.00	Ruby GF	a strong, fluorescent red-pink color	Madagascar
110		6.54 ct AA	$40.00	$262.00	Sapphire	a light blue to light purple change	Tanzania
111		5.92 ct A+	$85.00	$503.00	Ruby GF	a beautiful, strong, rich red color	Madagascar
112		4.55 ct AA	$30.00	$137.00	Sapphire	a medium-light blue, no change	Tanzania

Cutting and Polishing Sapphire and Spinel - Barry Bridgestock

Cutting and polishing sapphire and spinel need not be much more difficult than dealing with other gems. Cutters
should be aware of the fact that spinel and sapphire have a softer and harder cutting direction. Care must be taken
to prevent overcutting when cutting in the softer direction. An ink mark on the dop to indicate the softer direction can
serve as a reminder. After finishing the cutting of the facets on a broken-in solid steel Crystalite 600 lap, I prepolish using 14,000 Crystalite pump spray diamond and white vinegar sprayed on a ceramic lap. I prepolish until the 600 scratches and ALL pits are gone, leaving each facet with a greasy looking finish because of the fine 14,000 scratches.
I then remove these fine scratches using 50,000 Crystalite pump spray on a corian lap. I use bottled water from a spray bottle as a coolant and do not have to apply a thin coating of wax as suggested by the manufacturer of the corian lap.
Finishing the table facet requires one additional step. Linde A with a white vinegar spray on a different corian lap. Using the corian lap will preserve the facet flatness produced by the ceramic lap. Corian laps are available from the Jarvi Tool Company, maker of Facetron, and giving these stones extra brilliance. It pays to shop around for ceramic laps and it is not necessary to have the most expensive ceramic lap made for prepolishing with 14,000 diamond.

Please feel free to offer suggestions or additions. I don't think it's common knowledge that you can use Linde A to polish sapphire. I certainly didn't know it until I tried it out of shear desperation last summer.