Parsing inflected forms may not always work as expected. If the following does not give the correct word, try Latin Words or Perseus.
Ammōn, better Hammon, ōnis, m. [Egypt. Amun],  =  Ἄμμων, 
- I. a name of Jupiler, worshipped in Africa under the form of a ram (on the present oasis Siwah). Connected with his temple was an oracle often consulted by the ancients; cf. Cat. 7, 5 sqq.; Curt. 4, 7; Luc. 9, 511 al.
Whence Ammonis cornu, a gold-colored precious stone of the shape of a ram’s horn, ammonite, Plin. 37, 10, 60, § 167.
Hence,  
- II.  Ammōnĭăcus, a, um, belonging to Ammon (Africa, Libya): sal, Plin. 31, 7, 39, § 79; Col. 6, 17, 7; Ov. Med. Fac. 94.
Ammō-nĭăcum, i, n. subst., a resinous gum, which distils from a tree near the temple of Jupiter Ammon: Ammoniaci lacrima, Plin. 12, 23, 49, § 107: Ammoniaci lacrimae, id. 20, 18, 75, § 197: Ammoniaci guttae, Scrib. Comp. 28, 35; Cels. 5, 5. 
Hammōn (Amm-), ōnis, m.,  =  Ἄμμων, 
- I. an Egyptian and Libyan deity, worshipped (in the present oasis Siwah) in the form of a ram, and identified by the Greeks and Romans with Ζεύς and Jupiter; hence, Juppiter Hammon. Connected with his temple was an oracle often consulted by the ancients, Cic. N. D. 29 fin.; id. Div. 1, 43, 95; 1, 1, 3; Curt. 4, 7, 3 sq.; Luc. 9, 514 al. (cf. Cat. 7, 5).
Hence, Hammonis cornu, a gold-colored precious stone of the shape of a ram’s horn, Ammonite, Plin. 37, 10, 60, § 167.  
- II.  Derivv. 
 
- A.  Hammōnĭum (Amm-), ĭi, n., the oasis El-Siwah, Curt. 4, 7, 3 sq.
 
- B.  Hammōnĭi, ōrum, m., the inhabitants of Hammonium, Curt. 4, 7, 11. 
 
- C.  Hammōnĭăcus (Amm-), a, um, belonging to Hammon (Libya, Africa). 
 
- 1.  Adj.: sal, Plin. 31, 7, 39, § 79; Col. 6, 17, 7; Ov. M. Fac. 94.
 
- 2.  Subst.: Hammōnĭă-cum, i, n., a resinous gum, which distilled from a tree near the temple of Juppiter Hammon, Plin. 12, 23, 49, § 107; 24, 6, 14, § 23; Cels. 5, 5.