Eakle and Rogers — Wilkeite, a New Mineral. 263 



been much more intense and localized by the presence of small 

 dikes. This hill is locally designated as the Sky Blue Hill on 

 account of the presence of much beautiful blue calcite, and it 

 is in this blue calcite that the new mineral occurs, as well as 

 an abundance of garnet, vesuvianite and diopside. 



Both of the writers visited the quarries during the past sum- 

 mer and one of them (A. S. E.), in company with B. M. Wilke 

 of Palo Alto, made an extensive collection of specimens and has 

 in preparation a paper descriptive of the deposit. One of the 

 minerals collected occurred as an aggregate of pale rose-red 

 grains imbedded in the blue calcite and as it was unrecognized 

 in the field and thought possibly new, much of the mass con- 

 taining it was collected. Later analyses proved it to be a new 

 mineral and the writers take pleasure in naming it wilkeite in 

 honor of R. M. Wilke, who as a mineral collector and dealer 

 has done much to advance the science of mineralogy. 



Crystal Form. — Wilkeite crystallizes in the hexagonal 

 system and is prismatic in habit. The largest distinct crystal 

 observed measures 2 mm. by 5 mm. The crystals usually have 

 rounded faces and edges, a very common feature of minerals 

 imbedded in crystalline limestone. Most of them show one or 

 two faces of the prism, and a few were found with a complete 

 hexagonal zone, but the terminal faces are invariably rounded 

 and confused, so that good measurements of the pyramids 

 could not be obtained. Good readings were obtained in the 

 prismatic zone, some of the angles being exactly 60° between 

 the unit prism faces and 30° between (1010) and (1120). A 

 faint image _was also obtained for the form (31$0). Measured 

 (1010) : (3140) = 13° 46', calculated 13° 54'. The faces of 

 (1120) are very narrow and usually not present on more than 

 two or three of the edges. Some of the terminal faces give 

 good reflections which correspond in position to very steep 

 third order pyramids, but the readings do not correspond to 

 any probable forms. On one crystal a face in the vertical 

 zone with (1010) gave the angle p = 40° 9'. Assuming this 

 face as the unit pyramid, then the axial ratio for wilkeite is 

 approximately a : c == 1 : 0*730. This is based on the measure- 

 ment of a single face and cannot therefore be regarded as the 

 true ratio, but it shows that the axial ratio is at least near 

 that of apatite (c = 0*7346). 



Physical Properties. — Wilkeite has an imperfect basal cleav- 

 age and is very brittle. The hardness is about 5. The color 

 is pale rose-red* and varies from sub-transparent to sub-trans- 

 lucent. The luster is sub-resinous on a broken surface, while 

 the prism faces are generally very brilliant. The specific 



* A single specimen found later is yellow in color. This is a subhedral 

 crystal about 2 cm. in length. In physical and chemical properties it agrees 

 with the rose-red wilkeite and proves that the color is variable. 



