Material	S	Hard high	Hard low	SG high	SG low	RI high	RI low	Birefringence	Optic Sign	Disper - sion
RHODOCHROSITE		4.5	3.5	3.70	3.40	1.840	1.574	.201 - .220	U - A
RHODONITE		6.5	5.5	3.76	3.30	1.760	1.540	.010 - .014	B+ A
UNAKITE		7	6	3.20	2.85	1.760	1.520	-	A
CALCITE	*	3	3	2.94	2.65	1.740	1.486	.172 - .190	U- A	.017
MAW-SIT-SIT		6	6	3.15	2.46	1.74	1.53	-	A
GLASS	*	6	5	4.50	2.30	1.700	1.470	-	I	.009 - .098
PLASTIC	*	3	1.5	1.55	1.05	1.700	1.460	-	I
PEARL		4.5	2.5	2.85	2.60	1.690	1.530	.155 - .156	A
ARAGONITE		4	3.5	3	2.47	1.685	1.530	.155	B- A
SHELL, (sea)		3.5	3.5	2.89	2.70	1.685	1.530	.155	A
CALCAREOUS CONCRETIONS		4	2.5	2.89	2.18	1.685	1.530	.155	Agg
AMMOLITE		5.5	4.0	2.85	2.60	1.680	1.520	1.35 - 1.55	Agg
WITHERITE		3.5	3	4.79	4.27	1.677	1.529	.148	B -
VIVIANITE	*	2	1.5	2.68	2.64	1.675	1.569	.049 - .059	B+
HUMITE GROUP		6.5	6	3.35	3.15	1.674	1.563	.026 - .041	B+
AMMOLITE		4	4	2.95	2.70	1.670	1.520	.150	B-
STRONTIANITE		3.5	3.5	3.79	3.63	1.670	1.520	.150	B -	.008 - .028
APATITE	*	5	3	3.35	2.5	1.667	1.589	.001 - .013	U-	.013
WHEWELLITE		3	2.5	2.25	2.19	1.651	1.489	.159 - .163	B+	.034
TURQUOISE	*	6	5	2.90	2.40	1.650	1.590	.040	B+ A
WELOGANITE		3.5	3.5	3.20	3.10	1.648	1.558	.090	B -
PECTOLITE		5	4.5	2.90	2.74	1.645	1.595	.028 - .038	B+ A
TREMOLITE		6	5	3.20	2.90	1.643	1.560	.017 - .028	B -
GRANDIDIERITE		7.5	7.5	3.00	2.85	1.639	1.583	.039	B -
CHRYSOCOLLA Also see Chalcedony		7	2	3.2	2.65	1.635	1.544	.023 - .040	U+B- A
Material	S	Hard high	Hard low	SG high	SG low	RI high	RI low	Birefringence	Optic Sign	Disper - sion
AMBLYGONITE		6	5.5	3.11	2.98	1.633	1.578	.020 - .027	B+/-
EUDIALYTE		5.5	5	2.98	2.74	1.633	1.591	.003 - .010	U+/-
HAMBERGITE		7.5	7.5	2.37	2.35	1.630	1.550	.072	B+	.015
BRAZILIANITE		5.5	5.5	3.00	2.80	1.624	1.599	.019 - .021	B+	.014
CATAPLEIITE		6	5	2.80	2.65	1.624	1.596	.280	U+
HERDERITE		5.5	5	3.02	2.95	1.624	1.591	.029 - .030	B -	.017
PHOSPHOPHYLLITE		3.5	3	3.13	3.08	1.621	1.590	.021 - .033	B -
ANDHYDRITE		3.5	3	2.98	2.90	1.614	1.570	.044	B+	.013
COLEMANITE		4.5	4.5	2.42	2.35	1.614	1.586	.028	B+
MELIPHANITE (MELINOPHANE)		5.5	5	3.03	3.00	1.612	1.593	.019	U -
SUGILITE		6.5	5.5	2.79	2.68	1.611	1.590	.003 - .005	U- A
HOWLITE		3.5	3	2.58	2.45	1.608	1.583	.022	B- A
HURLBUTITE		6	6	2.88	2.80	1.604	1.595	.009	B-
WARDITE		5	5	2.87	2.81	1.604	1.586	.009	U+
BERYL	*	8	7.5	2.90	2.60	1.602	1.560	.004 - .009	U-	.014
PYROPHYLLITE		2	1	2.90	2.65	1.601	1.534	.050	B -
BRUCITE		2.5	2.5	2.39	2.30	1.600	1.559	.010 - .020	U+
EKANITE		6.5	5	3.32	3.28	1.600	1.572	.001	A U-
KAMMERERITE		2.5	2	2.64	2.55	1.600	1.597	.003	B+/ -
TALC		2.5	1	2.83	2.20	1.600	1.538	.039 - .050	B- A
VARISCITE	*	5	3.5	2.60	2.20	1.594	1.554	.031	B- A
NORBERGITE		6.5	6.5	3.18	3.15	1.593	1.563	.026 - .027	B+
XONOTLITE		6	6	2.71	2.60	1.593	1.583	.010	B+
AUGELITE		5	4.5	2.75	2.69	1.590	1.570	.014 - .020	B+
FELDSPAR		6.5	6	2.77	2.54	1.590	1.514	.005 - .010	B+/- A
Material	S	Hard high	Hard low	SG high	SG low	RI high	RI low	Birefringence	Optic Sign	Disper - sion
CORDIERITE	*	7.5	7	2.78	2.53	1.587	1.522	.005 - .018	B+/ -	.017
LEPIDOLITE		4	2.5	3.30	2.80	1.587	1.525	.018 - .038	B -
ZEKTZEROTE		6	6	2.79	2.70	1.584	1.582	.002	B -
SERPENTINE		6	2.5	2.80	2.44	1.574	1.490	.001 - .014	B+/- A
SHORTITE		3	3	2.60	2.50	1.570	1.531	.039	B -
BERYLLONITE		6	5.5	2.85	2.80	1.561	1.552	.009	B-	.010
CHAROITE		6	5	2.78	2.54	1.561	1.548	.009	A B+
WAVELLITE		4	3.5	2.36	2.25	1.561	1.520	.025	B+
MILLERITE		3.5	3	5.60	5.30	1.550	1.520
HORN		2.5	2.5	1.80	1.70	1.56	1.56	-	I A
THOMSONITE		5.5	5	2.40	2.25	1.555	1.497	.021 -.025	B+ A
QUARTZ	*	7	7	2.91	2.64	1.553	1.544	.009	U+ A	.013
MILARITE		6	5.5	2.61	2.46	1.551	1.529	.003	U -
CORAL, GILSON	*	4	3.5	2.44	2.44	1.550	1.550		A
LAZURITE	*	6	5	3.00	2.38	1.550	1.500	-	I A
PALYGORSKITE		4.5	2	2.21	2.1	1.550	1.550
TORTOISE SHELL		2.5	2.5	1.26	1.35	1.550	1.540	-	I
NEPHELINE		6	5.5	2.66	2.55	1.546	1.526	.004	U-
AMBER		2.5	2	1.10	1.05	1.545	1.539	-	A	-
STICHTITE		2.5	1.5	2.22	2.16	1.545	1.518	.027	U -
CANASTITE		6	5	2.71	2.60	1.543	1.534	.009	B-
MELLITE		2.5	2	1.64	1.58	1.541	1.509	.028 - .032	U -
COPAL		2	2	1.10	1.03	1.540	1.530	-	I
IVORY		2.75	2.25	2.00	1.70	1.540	1.535	-	A	-
ZEOLITE		5	4.5	2.5	2.30	1.54	1.53	.001 or less	U+/-
LANGBEINITE		4	3.5	2.83	2.75	1.536	1.536	-	I
GYPSUM		2	2	2.35	2.25	1.53	1.520	.090 - .010	A B+	.033
Material	S	Hard high	Hard low	SG high	SG low	RI high	RI low	Birefringence	Optic Sign	Disper - sion
LAPIS, GILSON	*	3	3	2.33	2.53	1.53	1.55	-	A
SELENITE		2	2	2.35	2.25	1.53	1.52	.090 - .010	A B+	.033
SLOCUM STONE	*	6.5	5.50	2.51	2.41	1.53	1.49	-	I
CANCRINITE		6	5	2.51	2.30	1.528	1.488	.002 - .022	U- /+	weak
KURNAKOVITE		3	2.5	1.85	1.78	1.525	1.488	.027 - .036	B+
POLLUCITE		7	6.5	2.94	2.85	1.525	1.518	-	I	.012
PETALITE		6.5	6	2.50	2.30	1.523	1.502	.012 - .016	B+
GAYLUSSITE		3	2.5	2.00	1.90	1.522	1.445	.077	B -
LAZERBLUE	*	6.5	6.5	3.93	3.93	1.520	1.520	-	A	Low
ULEXITE		2.5	1	1.95	1.65	1.519	1.496	.023	B+
GLASS, NATURAL		5.5	5	2.50	2.20	1.510	1.460	-	I
PROSOPITE		4.5	4.5	2.90	2.69	1.510	1.501	.009	B+ A
INDERITE		2.5	2.5	1.86	1.78	1.507	1.486	.017 - .020	B+
THAUMASITE		3.5	3.5	1.91	1.80	1.507	1.464	.036	U-
HAUYNE		6	5.5	2.50	2.40	1.505	1.496	-	I
YUGAWARALITE		4.5	4.5	2.25	2.23	1.504	1.495	.009	B+
TUGTUPITE		6.5	4	2.58	2.30	1.502	1.496	.006 - .008	U+/- A
LEUCITE	*	6	5.5	2.50	2.47	1.50	1.50	-	I U+